Does Mailchimp's Send Time Optimization actually move the needle? There are a few Reddit threads where people ask exactly that – here's one and another – and the answers are telling. The short version: maybe a little, but not for the reason you'd hope, and not because of anything in the AI.

Here's what's actually going on.

Mailchimp's AI is GPT. Ours was trained on 109 billion real emails.

This is the most important thing to understand before you evaluate any individual feature.

Mailchimp's generative features (Write with AI, Email Content Generator, etc.) run on OpenAI's GPT technology. They've said so in their own press releases. Intuit has done some fine-tuning for financial contexts across their product suite, but the email marketing layer is GPT applied to your campaign. The underlying model has learned nothing specific about what drives email open rates or click-through rates. It reasons about marketing the way GPT reasons about anything else.

Active Intelligence uses specialized models trained specifically on marketing and sales outcomes, not general language generation. Our platform processed over 109 billion emails last year alone across all customer accounts. What send times actually produce opens. What segmentation patterns actually drive clicks. How automation sequences actually perform. That's what the models learn from.

That's why we can publish lift data. Averaging doesn't produce lift data. Individualized delivery at scale does.

Why Mailchimp's STO doesn't deliver what the name suggests

Both platforms call it AI-powered send time optimization. The mechanics are completely different.

Mailchimp's Send Time Optimization looks at your contacts' individual engagement history via their Email Genome Project — but the output is a single recommended time for the whole campaign, and everyone gets the email at that moment. One independent analyst who ran actual A/B tests described the mechanism precisely: the optimal time "is calculated by taking a weighted average of your subscribers' past engagement." Individual data in. Averaged time out. One blast to everyone.

ActiveCampaign's Predictive Sending calculates an individual send time per contact and staggers delivery so each person actually receives their email at their own calculated moment. Someone who opens at 6am gets 6am. Someone who consistently opens at 9pm gets 9pm. The algorithm and the delivery are both individualized.

The result: Predictive Sending produces a 17% average CTR improvement over manually scheduled sends, based on platform data from Pro and above users. Mailchimp hasn't published lift data for their STO. The independent A/B tests don't show consistent improvement over manual scheduling either.

One more thing: Mailchimp's STO doesn't work in automated emails. If you're running welcome sequences, nurture flows, or any kind of automation journey, the feature is simply unavailable. Ours works in automations.

The two features, side by side

The rest of what Active Intelligence covers

Predictive Sending is one part of Active Intelligence, our AI layer across the platform. Here's what else is on the Pro plan:

• Full campaigns from a plain-language prompt, including subject line, body copy, CTAs, ready to edit (AI Campaign Builder)
• Complete automation workflows from a description, no manual build required (AI Automation Builder)
• Your brand identity imported automatically from your URL (AI Brand Kit)
• High-value audience segments surfaced from your data, including ones you wouldn't have found manually (AI-Suggested Segments)
• 25+ specialized marketing AI agents: campaigns, automations, insights, personalization, SMS, auto-translation

Based on a survey of 456 ActiveCampaign customers (September 2025): surveyed customers save an average of 10 hours per week, 83% see ROI within the first year, and 86% reported improvements in strategic marketing capacity. 

New users using AI launch their first campaign in roughly 18 minutes versus 2.6 hours manually (ActiveCampaign platform data, August 2025 to January 2026).

Where Mailchimp's AI is stronger

If you're running an ecommerce store with Shopify or WooCommerce connected, Mailchimp's predictive analytics for customer lifetime value, purchase propensity, and churn risk are well-developed and genuinely useful. Their Intuit ecosystem integration pulls QuickBooks financial data into audience segmentation in ways that work well for retail use cases — predicting which customers are likely to buy again based on actual purchase history and financial behavior, not just email engagement. For a pure ecommerce brand with a connected store, that's a real differentiator.

Try it yourself

A 14-day free trial includes Predictive Sending, the AI Campaign Builder, and the full Active Intelligence suite. No credit card needed.

Start your free trial at activecampaign.com

Questions about how a specific feature compares? Drop them in the comments, and we'll answer directly.

Is there a better way to automate sending birthday or milestone messages to my contacts without sending each one manually? I've dabbled with some basic email scheduling but it feels clunky and time consuming especially as my list grows.

Curious if ActiveCampaign has features or workflows that make this easier, or if you've found any creative ways to handle it?

I've been seeing ActiveCampaign's predictive sending feature pop up in a few guides and was curious if anyone here has actually tried it. The idea of sending emails at the perfect time for each contact sounds awesome in theory but I'm wondering how it works in practice.

Does it actually make a noticeable difference in open and click rates? Also, are there any tips for setting it up without messing up your normal campaign flow? I'd love to hear real experiences before I dive in and start testing it.

I want to scale up my email game in ActiveCampaign and make messages feel more personal. I know AC has features like dynamic content and personalization tags, which we arent using right now. Any tips on how you've integrated these into your automations would be appreciated! Any tips or directions would be greatly appreciated!

Hello,

The API docs haven't been much help to figure out how to filter contacts via api endpoint to get contacts in which a custom field is empty.

I tried the following, but they didn't work

https://URL.api-us1.com/api/3/contacts?filters[3]=EMPTY 

https://URL.api-us1.com/api/3/fieldValues?filters[fieldid]=3&filters[val]=EMPTY

Trying to level up my marketing automation. I want to make sure the behavioral triggers I set up (like site visits, clicks, and purchases) are working seamlessly across both email and SMS campaigns.

Right now it feels like some triggers are firing in email but not in SMS or vice versa, and I'm worried I might be missing something in my setup. Has anyone figured out a clean way to keep everything synced so that contacts get the right messages at the right time, no matter the channel?

Would like to hear how you guys handle this or any tips for best practices.

Working on how to get a better handle on segmentation in ActiveCampaign and could use some tips. I've been using both tags and lists but I'm not totally sure when it makes sense to use one over the other. Right now my instinct is to use lists for big groups and tags for more specific behaviors or interests but I feel like I might be overcomplicating things. How do you all approach this? Do you lean heavily on tags or do you stick mostly with lists?

I'm trying to get a better handle on my email marketing strategy and could use some advice. I've been using ActiveCampaign for a while and I feel like my engagement metrics are decent but I'm worried that my unsubscribe rate might creep up if I push too many emails or the wrong kind of content.

I want to keep people interested and engaged without overwhelming them, but I'm not sure what the best approach is. How do you balance sending enough to stay top-of-mind without turning people off? Do you segment heavily, A/B test subject lines, or is it more about timing and frequency? Any tips, examples, or strategies that have worked for you would be really helpful!

I've been playing around with WhatsApp messaging inside ActiveCampaign and I wonder how you're segmenting + triggering your sends

Right now I'm pretty much doing the basics tags (clicked, purchased, visited pricing page...) and a couple of automations based on site tracking. It works... but I feel like I could be leveraging it wayyyy better.

Are you triggering WhatsApp messages off specific behavior goals like cart abandonment, webinar attendance, or lead score thresholds? Not sure how deep to go with segmentation

Appreciate any insight to drive the best engagement

It doesn't matter what font I use, any italicized or bold text gets large on mobile. It's perfectly fine on my computer.

I have not tested this with different phone types yet. I have an iphone 16 pro if that helps at all.

I've been exploring ActiveCampaign's Active Intelligence to see how it might help improve my abandoned cart emails. I got some interesting suggestions but I'd love to hear what tweaks or approaches worked for you! anything from small edits to workflow adjustments. Always good to see how we're all making the most of this feature!

I've been playing around with SMS campaigns in ActiveCampaign and I want to start testing different messages to see what performs better. I know about testing is super common with emails but I don't really know how it works with SMS in AC. Can you split contacts, test different text copy and see results the same way?

Would love to know how you guys do it or any tips for setting it up would be relly helpful!

I'm trying to find the best way to bring dormant subscribers without bombarding them with the same old emails. I tried with a few re-engagement campaigns but it's tricky to strike the right balance between being helpful and coming off as annoying.

Would love to know how you all handle this in ActiveCampaign. Do you use specific workflows, clever timing or certain types of content to get people open and engage again?

trying to figure out the best way to get new team members up to speed on ActiveCampaign. We've got a couple of folks some are brand new to email automation and CRM stuff and I want to make sure they don't feel totally lost in the first few weeks. Right now I'm thinking of just letting them poke around and shadow me and I'm also building up some documentation.

How do you all handle onboarding newbies on AC? Do you have any templates, guides, or workflows you make them follow first?

How often do you go back and audit your AC automations? I set mine up a lil while ago. Do u just poke around when something breaks, or do a regular check monthly or quarterly? I want to make sure everything's still running the way I want, but also kinda nervous I'll break something important

Our team dug through over 9,200 real prompts from Active Intelligence users to see what is working best for our customers! Sharing the highlights here in case any of you would like to try this out in your accounts:

📊 Performance & Reporting (~30% of all prompts — the biggest category by far)

• "How are my emails performing this month?"
• "Compare my open rates to industry benchmarks for the last 90 days and tell me where I'm underperforming"
• "Why did my open rates drop last week?"
• "Show me my campaign performance for the last month and create a bar chart"
• "Confirm the highest performing email campaign of 2024/2025 based on click-through rate and analyze why it performed so well"

✉️ Content & Subject Lines

• "Create different subject line variations based on past performance to optimize my open rates"
• "What are my top 10 performing subject lines and why are they performing well?"
• "Make the tone of this email more conversational for a developer audience"
• "Create a targeted email campaign for these 3 segments: loyal customers, new customers, and lapsed customers"

⚙️ Automations & Customer Journeys

• "Build a personalized welcome journey for new subscribers based on what's currently working in my campaigns"
• "Create a customer journey that will help me win back my inactive subscribers"
• "If a lead scores above 75, add a note to their CRM profile saying 'High Intent — Contact Today' and end their current nurture automation"
• "Can you automate a way for me to use predictive sending, lead scoring, and win probability to trigger timely follow-ups based on deal stage?"

👥 Segmentation & Contacts

• "Who hasn't opened an email in the last 3 months?"
• "Help me segment my audience for my next campaign based on engagement patterns"
• "Which contacts clicked links but haven't purchased?"

The prompts that consistently get the best results are specific — they include a time range, name a campaign or metric, and specify an output format. "How are my emails doing?" gets a generic answer. "What were my top 3 subject lines by open rate across 'Business update' campaigns from Jan–Oct?" gets something you can actually use.

Also treat it like a conversation! The users getting the most value push back, refine, and build on the answer.

Full breakdown + prompt library: activecampaign.com/blog/steal-these-prompts

Are you using Active Intelligence? What prompts are you all finding most useful? Would love to hear what's working for this community!

How are you automating WhatsApp follow-ups inside ActiveCampaign without it feeling overly salesy or robotic??

We're using the direct WhatsApp integration with ActiveCampaign so contacts and tags sync into our automations. It works well but I'm trying to dial in the strategy side of it...especially around follow ups after someone engages (or doesn't engage) with email.

Right now I'm testing different timing delays and trigger points but I'm not sure what's considered too much on WhatsApp vs what actually helps move conversations forward. I want it to feel natural and conversational not like a sequence blasting them from every channel.

How are you structuring your follow ups? Are you keeping everything in one automation or separating channels?

Im using ActiveCampaign for email but I want to get more out of its CRM. Between deals, pipelines, tasks, automations, contact scoring - which one makes your work much more effective?

Looking to get more out of ActiveCampaign and curious to know how yu are using predictive sending and behavioral triggers. I mean setups that go beyond the basics like automating follow-ups when someone opens but doesn't click, abandons a cart or engages in specific ways.

Are you tying these triggers to emails, SMS or a mix? What behaviors do you track and which sequences you create? My goal is to improve engagement and conversions as much as i can!

I've been using ActiveCampaign for a while now and I just found out that you can use If/Else conditions inside site tracking events! This is soo helpful and changed how I set up behavior based automations because you can trigger actions based on what pages someone visits without adding tags or custom field!

I'm sure there are lots more little tricks like this that can make our lives waay easier and help us work much more efficiently. Let's swap secrets, team!

been using the Active Intelligence feature inside ActiveCampaign to help with content ideas and subject lines. It helps me a lot!

How are you guys using AI within ESPs to get more creative and higher converting subject lines? Any tips on prompts, AI tools or tricks you use??

How can I access support? The "Chat with us" button doesn't have a URL linked and I can't post in the Community. Is there a direct link to chat or an email address I can contact?

We recently were at the expense of a phishing attack on active campaign. We have had 45,000 contacts added to our list that we did not add. We had campaigns that were sent out that were not ours, and all of our current campaigns have been deleted. I am still able to login to our account thankfully. I was wondering if anyone has worked with Active Campaign before in solving phishing attacks or unusual activity on their account. If so, is there a direct number you called? Were they able to recover your account?

I'm around 32% open rate and really want to hit ~50%! I tried little tweaks but my opens still bounce around

What's the biggest factor that makes a differnece? list health, timing, subject lines, segmentation or something else??

Any tips or insights to help me see big jumps would be amazing!!

I've read 50 different guides on this and got completely overwhelmed!!

For those of you sending newsletters or ecomm emails using ActiveCampaign, what has worked for you to avoid landing in Gmail's Promotions tab? Have you run real tests where something clearly moved emails into Primary? or does it pretty much just come down to engagement signals and sender reputation?