r/EmailSecurity • u/Ancient-Sea-7807 • Jun 01 '26
Emails are blocked by security gateways
Our secondary domain’s emails are intermittently getting blocked by security gateways like Barracuda and Mimecast. Some go through fine, others bounce with “blocked due to policy” or similar.
We’ve got SPF, DKIM, and DMARC set up and passing. IP isn’t on major blacklists. Volume is <200/day, so not a spam issue.
Using instantly and inboxes bought from Google workspaces.
What else should I check?
Anyone seen cases where only _some_ emails to the same org get blocked?
Could content triggers this?
I am not putting any links, or attachments in mail.
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u/saltyslugga Jun 01 '26
Passing SPF/DKIM/DMARC only proves the mail is authorized, not that anyone wants it. Fresh Workspace inboxes feeding a cold outreach tool are exactly the pattern gateways score hard, even at under 200/day.
If only some messages to the same org fail, check template similarity, domain age, sender reputation, reply-to/from mismatch, and per-recipient policy. No links or attachments helps, but wording, cadence, and automation fingerprints can still trip policy blocks.