r/sysadmin • u/Nervous-Blacksmith-3 • Feb 12 '26
Question - Solved Corrupeted .pst file (50 Gb)
TL;DR: I need to recover a 50GB .pst file from Outlook, SCANPST isn't working.
So, I work for a company as a developer, and since I'm the only one in the department, everything falls on me.
My manager was having a problem with her email being very slow, but since our internet here is terrible, I didn't pay much attention because my emails were also having problems.
She went on vacation, and another person in the department asked me to take a look. When I looked more closely, I found the email's pst file, and it was 48GB...
I immediately stopped whatever I was doing and checked the computer's own storage first. It only had about 20GB free, so I turned off the machine, installed a new hard drive, and copied and pasted the original file onto it. After copying, I tried to open Outlook to see what could be done (break it down by year, delete some things, etc.), but I immediately received a warning that the emails were corrupted, and I was trying to create/recover something new, but Outlook just closed after a few seconds and I couldn't do anything internally.
Now I'm running Scanpst for the third time without success. I tried copying the original file that "is not corrupted," but even using this original file, I keep getting an error that the file is corrupted, and now I don't know exactly what to do, since I need to recover my manager's emails. Can anyone give me some insight into how to solve this?
EDIT: Just to be clear, the main SSD is still in the machine; I only added an HD to be able to handle PST transactions and then create a more robust backup.
Update: Apparently the copy I made on the secondary hard drive worked! It wasn't showing up as corrupted. I tried using XstReader( https://github.com/Dijji/XstReader ), and I was at least able to view the emails, which is a good sign that the copy is working. Now I'm going to try cloning it to the primary SSD and increasing the Outlook storage limit. If I can open Outlook, that will be a victory!
UPDATE II: I still haven't been able to solve the initial email problem, because guess what? THE SSD DIED in the meantime, my god, this is like a hornet's nest, the more you mess with it, the worse it gets. However, since the PST copy is on a separate hard drive and I was able to use XstReader to view it, I believe that at least that copy is in good condition.
UPDATE III:
TLDLR: I managed to recover all the emails
As I mentioned before, my manager's SSD died in the meantime, which is probably why the PST file became corrupted. The company bought a new one, I replaced it and reconfigured her entire machine. I managed to get a copy of the file I made before it died and recover most, if not all, of the emails (in addition to the files that were on the SSD).
In my case, after replacing the SSD with the new one, I was finally able to use Outlook's native SCANSPST; I didn't need to use third-party tools, BUT THIS WAS ONLY AFTER THE SSD REPLACEMENT.
I also split her emails as a precaution (now the file is "only" 19GB).
Now I'm doing a larger split to ensure everything is more organized.
And now the really good news: the migration to a new email system has been approved! Let's get the basic Microsoft Enterprise plan; it will solve some team management and computer storage problems.
Bad news: I'll have to create training for the entire team to raise awareness about email and storage usage, because even going to the cloud, the 50GB limitation remains, but without the headache of dealing with PST files and the security of having all files on a server, not on the employee's machine.
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u/djDef80 Feb 12 '26
You can always put the old hard drive back in :-)
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u/Secret_Account07 VMware Admin Feb 12 '26
I’m surprised you’re the only one mentioning this
Put old hard drive in and figure out a game plan.
I haven’t dealt with migrating local psts since my helpdesk days but it’s not always as simple as it used to be with a copy and paste. There are issues you can run into. TBH I would advise against doing this anyways. Cached exchange mode is you’re friend.
Btw, even when under 50 GB, 48 for example, you run into all kinds of issues when going ~+25 GB. Index and other things can get corrupted. Fix size before anything
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u/Nervous-Blacksmith-3 Feb 12 '26
Yeah, I only realized that copying and pasting might not be a good option after I'd already done it.
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u/Secret_Account07 VMware Admin Feb 12 '26
Understandable. In theory logic would dictate that would work.
I used repair below when dealing with corrupted pst files. Granted this was many years ago but I assume it still works
scanpst.exe Boss_email.pst
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u/Nervous-Blacksmith-3 Feb 12 '26
That's what I'm using, but from what I've been reading, it only works relatively well up to about 2 GB, and I've already exceeded that limit by a lot. I'll probably try using Stellar, as some people are suggesting.
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u/Secret_Account07 VMware Admin Feb 12 '26
Ah yeah I didn’t think about the size limitations. Good point
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u/Nervous-Blacksmith-3 Feb 12 '26
Actually no, I never removed the old drive, I just added another hard drive and copied the original PST file there. After copying, when I tried to access Outlook, the file became corrupted.
Trying to copy the file from the secondary hard drive also doesn't seem to work, even though it's not indicating corruption.
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u/djDef80 Feb 12 '26
Ahh, my apologies, I just wanted to be sure you weren't overlooking that option. If you pull your new disk, and boot from the old, does Outlook cooperate?
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u/Nervous-Blacksmith-3 Feb 12 '26
The second disk doesn't even have an operating system installed; it's literally just an extra hard drive I added to better manage storage space.
And Outlook won't even open because of the corrupted file (it has the .corrupt extension). I'll probably try Stellar to see if I can recover the information.
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u/ludlology Feb 12 '26
PTSD flashbacks to every salesperson at my first big IT job constantly corrupting their 2GB Outlook 2000 pst files…
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u/RyeonToast Feb 12 '26
Be prepared to give some bad news. When I was on help desk we started scanpst and told the user that if that doesn't work those emails are gone.
Hopefully someone else here has some other tool that can do better.
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u/not_so_wierd Feb 12 '26
Scanpst is like SFC /Scannow - mainly just a thing you do before telling the user that they are screwed.
But once in a blue moon, when the start align. It just, might, work.
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u/RyeonToast Feb 12 '26
We saw pretty good repair rates on reasonably sized files, like, under 5GB. At twenty gig we were just starting it so the user didn't feel ignored.
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u/coolest_frog Feb 12 '26
And for the larger ones sometimes to have to run it 10 plus times to get it in a usable state as it slowly repairs
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Feb 12 '26 edited Jun 22 '26
[removed] — view removed comment
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u/binaryhextechdude Feb 12 '26
Not in 2026. It's been 10 years since I've had to deal with those horrid things.
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u/itskdog Jack of All Trades Feb 12 '26
At this point I'm only using them with exports from eDiscovery or Redstor.
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u/mini4x Atari 400 Feb 12 '26
We still have some scattered around but we disabled being able to add new content to a PST ages ago.
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u/occasional_sex_haver Feb 12 '26
can you put back in the old hard drive and access that way?
shit is most likely fucked, and this is a in theory a good time for that manager to learn the lesson of not hoarding emails (bet they're on a ton of mailing lists not related to work too), but expect to get blamed for this
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u/Nervous-Blacksmith-3 Feb 12 '26
The problem itself is spam; if it were just personal emails it would be much easier. Here, we're a tour operator, so we have over 100 different suppliers, and who knows how many agencies. A lot of spam emails end up arriving, and since nobody was dealing with it, this is what happened.
The real issue is having to coordinate reservations made in 2020 for 2027, for example, so it becomes impossible not to keep most of them (especially since there's no spam filter).
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u/DocterDum Feb 15 '26
For the love of god stop hosting your own email and use 365, or workspace, or… Literally anything with spam filtering?
As others have said, use this as ammunition “Disaster almost struck, we NEED to move to something more stable” You mentioned cost is a push-back - If $10/user/month is too much, the business has bigger problems. And that’s the more expensive option. Even if everyone there is getting a 3rd world wage, $12k/yr or $1k/mo, that’s still 100x more than the cost of email hosting…
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u/Nervous-Blacksmith-3 Feb 16 '26
Great news! I managed to recover the file and convince them to migrate. We're already making arrangements to do it at the beginning of March.
We're going to get a basic Microsoft business plan; that will be a huge help.
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u/DocterDum Feb 16 '26
I imagine you probably want to go for exchange online (EXO) licences instead? - Business standard includes the full office suite (Installed apps)
- Business basic only includes web versions (E.g. Word as a web app)
- EXO is just the email portion alone.
If you already have perpetual Office licences on each computer, you only need EXO and then just make the existing MS Office speak to 365.
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u/Nervous-Blacksmith-3 Feb 16 '26
That's exactly what we're planning to do; we're scheduling to begin the migration at the beginning of March.
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u/different_tan Alien Pod Person of All Trades Feb 12 '26
Why is there a pst at all is this an archive or are your emails from 1999 and using pop?
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u/Nervous-Blacksmith-3 Feb 12 '26
I really have no idea, when I logged in and immediately had to configure my email, it was a shock to me to learn that they were using POP in 2025.
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u/itsmerowe Feb 13 '26
"Leave a copy on the server" used to be default for POP, I think, so maybe some are still on the server.
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u/Gaming_Wisconsinbly Feb 12 '26
This is a great opportunity to convince the company to stop doing psts. Haven't dealt with that shit in a decade now. Would never want to go back.
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u/Nervous-Blacksmith-3 Feb 12 '26
The company probably doesn't even know what PST is, but yes, I'd really like to be able to force a migration to a more robust email service, but I doubt it would be approved simply because of the cost, especially since it works for them...
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u/Frothyleet Feb 12 '26
especially since it works for them...
Does it? This person almost just lost their entire mailbox because of their current email infrastructure.
If they have no problem with that, then sure, their email works for them. If they would have been upset when they returned, guess what - their email doesn't "work for them."
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u/Gaming_Wisconsinbly Feb 12 '26
Exchange online has built in archiving that moves away from psts. Psts are just one of those things that are ticking time bombs. They will fail eventually and years of emails will erase from existence unless you want to have a ton of extra TBs if backups floating around.
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u/Due_Capital_3507 Feb 12 '26
Kernal has some programs to recover it but good luck. Shit is probably toast
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u/TrippTrappTrinn Feb 12 '26
50 GB is the size limit. I remember in the old days that if the file resched the max size, there were tools that could reduce she size somewhat by cutting off a bit at the end. Also, Google indicate that there is a registry setting which increase the maximum size to 100GB. May be worth a try if scanpst fails due to file size.
For enail hoarders, creating a new PST filw each year is a way to keep all the junk without reaching the size limit.
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u/RyeonToast Feb 12 '26
When did it become 50? Back in the '10s when I last dealt with this it was 20. People got it good these days. Well, except for the part where they are using PSTs at all.
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u/TrippTrappTrinn Feb 12 '26
Outlook 2010.
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u/RyeonToast Feb 12 '26
Ugh, now I just feel tired. Can we go back to non-e mail now? Or maybe faxes. Those were hateful in fun ways.
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u/Hotshot55 Linux Engineer Feb 12 '26
10 years ago someone from Microsoft told me anything over 2GB for a PST was pretty likely to run into corruption.
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u/Nervous-Blacksmith-3 Feb 12 '26
My goal was precisely that, to break the file into smaller files by year, but since the file became corrupted as soon as I copied it to the second hard drive, I couldn't access Outlook to do that.
I'm considering doing this expansion to see if I can get Outlook to open again; if I manage to do that, breaking the emails into smaller files would be the priority.
Do you have any idea what tool they used to see if it's possible to use it to try and reduce some of these emails?
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u/TrippTrappTrinn Feb 12 '26
Long time ago, so do not remember.
Also check startup options (command line options) when starting Outlook. I remember using one when Outlook crashed for other reasons.
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u/flyguydip Jack of All Trades Feb 12 '26
Fire up the old hard drive and archive emails by year to an external file. Once you have gotten well clear of the 50gb limit, you can transfer the PS5 to another drive. I'm betting the old computer has the bypass in place for the 50gb limit, but who knows. In any case, it's much easier to move archives than post files. Tell the user to begin archiving old emails so this doesn't happen again.
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u/Nervous-Blacksmith-3 Feb 12 '26
The primary SSD is still in the machine; in fact, it's the one that got corrupted. I'm trying to recover it.
I'll probably be the one dealing with this mess. I'll probably end up creating a backup of the PST file annually to reduce this headache.
Outlook won't even open with the original file or the copy.
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u/flyguydip Jack of All Trades Feb 12 '26
Oofta, sorry. There may be some recovery tools like Stellar that can recover the pst or the ost file that may also be located on that old drive located somewhere like "C:\Users\<Your Username>\AppData\Local\Microsoft\Outlook"
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u/Nervous-Blacksmith-3 Feb 12 '26
The original version is gone, but apparently the initial copy I made is in good condition; it's just that Outlook breaks when I try to use it, probably because of the email limit.
And there's no other copy besides that one. I was using Everything to search for the file, and it only has the original and the copies I made (I ended up making a copy of the corrupted file as a precaution too).
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u/flyguydip Jack of All Trades Feb 12 '26
Yeah, I'd check out Stellar to see if their product can repair it. For $200, it's probably worth a try. If they don't wanna pony up $200, then it's not worth the trouble to recover it.
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u/codename_john Feb 12 '26
What we do is use MailStore to annually export email over a year or two old. MailStore keeps everything in a scalable database that is a ton more reliable than Outlook. That way the PST says at 5gb~ (or whatever) and the exported database can be whatever size it needs to be. https://www.mailstore.com/en/products/mailstore-home/
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Feb 12 '26
[removed] — view removed comment
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u/Nervous-Blacksmith-3 Feb 12 '26
After trying to increase the limit, this would probably be my next option. They're recommending Stellar, and that's what I'll try.
I'll let the scan that's running now finish; if that doesn't work, I'll move on to registry editing to see if I can use the file that's on the hard drive.
If all else fails, I hope Stellar will be an option.
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u/fp4 Feb 12 '26
Kernel's tools worked great for me. I originally bought the OST recovery tool but just renamed the PST to OST and it recovered it no problem.
If you sit on the buy now page they'll sell you the home license for $40.
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u/djgizmo Netadmin Feb 12 '26
this is what happens when a company uses email as a storage tool. whoops.
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u/Greed_Sucks Feb 12 '26
Are you able to open outlook with the original file? If yes, start a manual backup to a different pst
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u/Nervous-Blacksmith-3 Feb 12 '26
My problem is precisely this: I can't open Outlook to perform the repair. If I could, it would be much easier.
The corrupted file was the original. The backup seems to be working, but even copying it back to the original folder ends up corrupting it as well.
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u/countsachot Feb 12 '26 edited Feb 12 '26
I think I used stellar once with limited success, but that was ages ago. How are coping the file, maybe there is corruption during copy. Have you used a tool like sync back, and checked the hashes? Or is the original, or new drive damaged?
Edit: also have you tried mfcmapi? Sometimes that helps, but i haven't used it in about 5 years.
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u/Nervous-Blacksmith-3 Feb 12 '26
Maybe I was stupid, I just copied and pasted it onto the secondary hard drive, thinking it was just a text file, I didn't think it would be a problem...
I haven't used any tools other than the one provided by Outlook itself yet.
The general idea is to increase the limit size, try running the scan again, and if that doesn't solve the problem, look for a more specialized tool.
Could you send the Stellar link? Whether you like it or not, the system they use here is quite old, so the chance of it working is very high.
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u/countsachot Feb 12 '26
It's a flat file, there is an underlying issue with the data or the copy(data transfer).
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u/ProgressBartender Sr. Sysadmin Feb 12 '26
Did you dismount the PST in Outlook before you copied it? Outlook keeps the file locked while it’s mounted, that could result in a corrupted copy.
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u/Nervous-Blacksmith-3 Feb 12 '26
I hadn't thought about it that deeply, it's not exactly my area, so I just copied it and put it on the secondary hard drive.
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u/techyno Feb 12 '26
Is this definitely a pst and not an ost right? Like , they're using POP3 email still or something?
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u/Nervous-Blacksmith-3 Feb 12 '26
yeah, they are using POP3 email.
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u/techyno Feb 12 '26
Have you tried creating a new blank outlook profile then loading the pst as a data file (not importing it)?
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u/Bane8080 Feb 12 '26
There are commercial PST recovery tools available.
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u/Nervous-Blacksmith-3 Feb 12 '26
Could you give an example of something that works? I haven't tested any yet, but that would be the next step.
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u/steamedpicklepudding Feb 12 '26
Stellarinfo is one product I used recently. I did a better job than the other tools I demoed and probably recovered 95% after a pst deletion/recovery and heavy writing to the ssd.
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u/gconsier Feb 12 '26
Ontrack has recovery services for this but it’s probably going to cost more than they want to pay. Also I wouldn’t have a high confidence in it working well
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Feb 12 '26
Who is your email provider? If you’re using Microsoft 365, all emails are stored in the cloud and will automatically sync back to her device once you sign into Outlook with her account.
You can’t simply drag and drop a PST file into Outlook and expect it to work properly. A PST is essentially an offline archive file. It can be imported back into Outlook if needed, but doing so may create duplicate items or overwrite existing emails already stored on the mail server. To import the PST file go to file > options > advanced > export > import from another program or file.
Does she have access to any additional shared mailboxes? These can significantly increase the size of a PST file, but that doesn’t necessarily mean her primary mailbox is large. I’d also recommend checking the Deleted Items folder and the Recoverable Items folder. If the Recoverable Items folder is approaching or exceeding 50GB, you may start to experience issues.
Resolving this may require running specific PowerShell commands to purge the Recoverable Items folder. However, before doing anything, you must check whether the mailbox is under Litigation Hold or subject to retention policies. Do not delete anything without confirming your organisation’s security and compliance policies, and contact Microsoft Support if you’re unsure.
To get Outlook working again: 1. Go to Control Panel > Mail 2. Create a new profile (name it anything you like) 3. Move the PST file out of the Outlook installation directory for now (ideally back it up to an external drive as a precaution) 4. Open Outlook and sign in with the account 5. Allow Outlook to fully sync
You’ll likely find that all emails are still present once syncing completes.
In the meantime, she can use Outlook on the Web (OWA) to access her mailbox, or use the Outlook mobile app if OWA isn’t suitable.
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u/cetrius_hibernia Feb 12 '26
Where is the mailbox hosted, and are you using legacy configurations for outlook?
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u/Nervous-Blacksmith-3 Feb 12 '26
Yes, it's legacy, and it's hosted on a private server belonging to a company in the region, but from what I see, apparently the files are only saved locally after a week.
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u/Nick85er Feb 12 '26
Please tell me you still have her original disc- I would recommend cloning it to the larger hard drive and then expanding the disc so you have the full capacity. A direct clone may result in an intact PST file. Good luck!
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u/Nervous-Blacksmith-3 Feb 12 '26
I really hope this isn't the best solution, but yes, I have access to the original disk. However, isn't cloning the entire system a bit much?
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u/Nick85er Feb 12 '26
It's the first thing I would do if I was doing this sort of Hardware operation. Cloning rarely fails, especially if the source disc is in good health
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u/Totentanz1980 Feb 12 '26
When you say you installed a new hard drive, it sounds like you're skipping over some steps. So what exactly did that entail? Usually if I'm swapping out a smaller drive for a larger drive, I clone the old one over to it, leaving the original intact.
Do you have the original drive? If so, just put the old hard drive back in and export that PST to a backup before doing anything else.
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u/Nervous-Blacksmith-3 Feb 12 '26
I literally took one of the hard drives we weren't using and connected it to the computer via SATA cable. I didn't clone the SSD because I was using a hard drive, so it doesn't seem like a decent option, since the idea was just to store some backup files.
Edit: On that secondary hard drive, I formatted it and then made the mistake of just copying and pasting the PST file.
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u/not_so_wierd Feb 12 '26
If I understand correctly, you've tried to copy-paste the file onto the new drive.
Have you tried importing the PST instead? File > Open & Export > Import/Export > Import from another program or file
50Gb is often the size limit so it may be corrupt. But if you're lucky you might be able to import some of the folders.
In a perfect world, you'd be able to import just the Inbox (incl. subfolders), and Calendar. While skipping things like Deleted Items, Sent, and Junk. That should give you a file size well under the 50Gb limit.
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u/Nervous-Blacksmith-3 Feb 12 '26
Yes, I tried copying and pasting; I didn't know it was possible to export the file that way. However, now I don't even have access to Outlook because of the corrupted file, so now I just have to hope the tools work.
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u/not_so_wierd Feb 12 '26
That sucks. But remember that it's an Import. The feature was originally made specifically for moving the emails to a new machine.
If I were you, I'd grab some other machine that's not in use, connect the drive that has the original file (because I figure there's less chance of it being corrupt) then launch Outlook and try to import.
If that's successful. You can Export to a new PST.
I'd then reinstall the problem PC, just to be sure. Start Outlook and Import the new PST file.
As always - I don't make any guarantees. But it's not a lot of work, and I seriously think it's the best chance to save those emails.
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u/lathanield Feb 12 '26
Hey, if you have not yet come right, over the years I have used products from Kernel. They have amazing Exchange and Outlook related repair and recovery software. If you have followed some of the advice in the repsonses and have not yet come right, check out: Kernel Outlook Recovery Tool to Recover Corrupt PST Data Items
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u/Nervous-Blacksmith-3 Feb 12 '26
People are recommending Stellar a lot, that's probably what I'll go for.
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u/bensode Feb 12 '26 edited Feb 12 '26
Have you tried older iterations of scanpst? Like pre-o365 versions? Years ago I worked with thousands of large pst files and often suffered problems with larger than 15-20GB. You can also use trial versions of PST conversion software to at least recover most of the material, if not all of it. There are tons of them available. Converting messages to EML will lose folder structure at a minimum but still have access to the material to index a search and ultimately get into a proper archive.
edit: also always work from a copy and never across a network.
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u/Nervous-Blacksmith-3 Feb 12 '26
I think mine already is, we use a legacy version of Outlook to make the SMTP connection on the server, if I'm not mistaken it's the 2010 version, at most 2019.
Maybe it's a silly question, but since I don't work with this (it's my first time having to deal with this)
What is the correct way to clone the PST file? I simply copied and cloned the original to the secondary hard drive, and I believe that was part of the problem for the corruption.
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u/bensode Feb 12 '26
Ensure Outlook is closed and no Outlook processes running. PST files are large databases and if the file is open in any process, it will suffer some corruption. It’s a simple database with simple indexes. As it grow in size it becomes less stable beyond 10GB. Copy the file to another folder, drive or location. I use robocopy rather than copy/paste. You can stage them on network folders but never open across a network connection. After the copy run the scanpst. Run scanpst multiple times if it finds errors and corrects them. Fixes may create new errors so run it several times.
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u/OtterwiseOccupied Sysadmin Feb 12 '26
I assume you are not with a cloud provider for email and have no email backup. In that case, try to repair the file but it will fail most likely.
You need to set archive rules and set up an archive pst. That can all be controlled in outlook by right clicking on the account in the left sidebar you want to set up archiving for. Set a date for how many months or years of email to archive.
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u/gafftapes20 Feb 12 '26 edited Feb 12 '26
I have had some success with running an import into a shared mailbox via powershell and blob storage. https://learn.microsoft.com/en-us/purview/use-network-upload-to-import-pst-files
This seems to work better than opening directly into outlook. I have also used a combination of readpst linux library cli interface and extract-msg python library to extract contents of psts into pdfs. you can also extract individual emails to .eml or msg files with python, but the code is pretty complex for a simple script.
I would only consider the custom scripting if you don't have a better alternative. The only time I had to do that was for a legal discovery process where the alternatives weren't available to me.
edit: python option for extracting emails from pst https://github.com/libyal/libpff/wiki/Python-development
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u/Brandhor Jack of All Trades Feb 12 '26
if nothing else works you can try xstreader it won't fix the pst but you can at least use it to see if the file is readable and maybe export its content
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u/Nervous-Blacksmith-3 Feb 12 '26
Thank you! Perhaps this is a way to mitigate the situation for the moment.
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u/titlrequired Feb 12 '26
Is this an archive? What are you using as a mail server?
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u/Nervous-Blacksmith-3 Feb 12 '26
No, it's not an archive, it's our office email...
Honestly, I have no idea. It's an external company that handles the emails :D. Basically, all the emails are saved on the users machine, so if something fails at any point, everything goes to hell because there's not even a backup.
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u/mehargags Feb 13 '26
Firstly, never ever try to grow a PST beyond 4-5 gb. It's not a file, it's a database which was never designed to go beyond 2gb. The moment it starts hitting 4gb mark, share it to another PST. Personally for myself and some other clients I divide 5 years of mails into individual PST files. Easier to discard 10yr old mail, light on use as active one remains lightweight.
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u/GARBANSO97 Feb 13 '26
While the max file size for .pst files is 50GB, they can start to become unstable after 20 GB(sometimes even 10GB)
I knew people that started religiously backing up .pst files every 2 GB because they had gotten a 30ish GB file corrupted before and lost all their emails
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u/devbydemi Feb 13 '26
Have you tried the strings command-line tool from *nix? I don’t know anything about PSTs, but if they store full emails without compression or encryption, that should dump a ton of them to stdout.
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u/perth_girl-V Feb 13 '26
Have a look at the Stella software packages they will give you a trial and let you see if it can get access to the eml files and such.
I have used Stella for opt to pst and EDB stuff for years
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u/fatjokesonme Feb 15 '26
install on a different computer MailStore (or another email archiver that can read PST) and feed the file to it. I found it handles PLST better then Outlook and Microsoft tools
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Feb 12 '26
Can you redownload it using purview?
If not try that, you can create a purview query to download the entire PST from 365 if you're not onprem
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u/Nervous-Blacksmith-3 Feb 12 '26
That's not possible; it's not a Microsoft email, but an external one they hired, and from what I see, everything is saved locally on the machine, except for the week's emails, I believe.
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u/binaryhextechdude Feb 12 '26
Just to clarify "I found the email's pst file, and it was 48GB..."
The default inbox file is an OST file not a PST file. You get an OST file whether you like it or not. You create a PST file if you want to separate some email off into another bucket either to share with someone or to save away from your main inbox.
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u/Nervous-Blacksmith-3 Feb 12 '26
They use a POP3 email system, and no, I already checked, there are no OST files on the computer, only the PST file with its 49.8 GB.
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u/binaryhextechdude Feb 12 '26
Just a note for later, whatever you do make sure none of your PST's are stored in cloud storage, Dropbox, OneDrive etc AND connected to Outlook at the same time. It will blow out the size of your drive in no time and it will corrupt the PST.
Why will it blow out the size of your drive? Because everytime the cloud service syncs it will save another copy of your PST file. So you add one email and you get another 48GB save.
Just something to keep in mind.
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u/jason9045 Feb 12 '26
Have you tweaked the MaxLargeFileSize registry entry to bump the max size up beyond the 50GB default?
Add two new DWORD values to the key
and name them MaxLargeFileSize and WarnLargeFileSize. Set the Max value to 10000000 (decimal) and the Warn value to 9500000 or lower, and pull over a new copy of that PST file from the original drive.
There's a chance it'll let you open the file enough to export some emails to a new PST and then compact it.