That's the call I get. The pattern is always the same. Open rates fall. Gmail starts routing half your sends to promotions or spam. The operator checks their automations, reviews their copy, maybe even re-writes a subject line or two. Nothing moves.
The problem isn't your automations. It's your sender reputation. And in most cases, it slid because of one of four things: you ramped volume too fast, engagement dropped in your active segment, your authentication broke, or a new content pattern tripped a spam filter. The good news: you can diagnose which one in ten minutes. The better news: the fix hierarchy is clear once you know what broke.
Pull Your Gmail Postmaster Data First
If you send any volume to Gmail addresses—and you do—this is step one. Go to Google Postmaster Tools and add your sending domain if you haven't already. You need to verify via DNS, but it takes two minutes.
Once you're in, look at two charts: IP Reputation and Domain Reputation. If either shows "Low" or "Bad," you've found the problem. If both show "High," your reputation with Gmail is fine—move to the next section.
Now check the Spam Rate chart. This is the percentage of recipients who manually marked your mail as spam. Anything above 0.30% triggers throttling. If you're sitting at 0.50% or higher, Gmail is already deprioritizing your sends. You need to pull back volume immediately and tighten your engagement targeting.
The User-Reported Spam Rate is the single clearest diagnostic you have. If it's elevated, your list hygiene or your content is the problem. If it's clean but your reputation is still bad, the issue is likely authentication or a sudden volume spike.
Check Authentication Next
Your domain needs three records configured correctly: SPF, DKIM, and DMARC. If any of these are missing or misconfigured, mailbox providers assume you're a spammer and route you accordingly.
Go to MXToolbox and run a lookup on your sending domain. Check SPF, DKIM, and DMARC status. All three should return green. If DMARC is missing or set to p=none with no reporting, you're leaving the door open. Set it to p=quarantine or p=reject and configure reporting addresses so you can see who's trying to spoof your domain.
If you're sending through ActiveCampaign's shared infrastructure, make sure ActiveCampaign is included in your SPF record. If you're on a dedicated IP, your DKIM signing domain should match your From domain. Mismatches here look like phishing attempts to spam filters.
The authentication fix is technical but straightforward. If your records are broken, fix them before you do anything else. No amount of engagement optimization will overcome a missing DMARC policy.
Pull Engagement by Cohort
This is where most operators skip the work—and that's why they can't diagnose the drop.
Open ActiveCampaign and segment your list by engagement recency. Create three segments:
- Engaged in the last 30 days: opened or clicked any email in the past month
- Engaged 31–90 days ago: opened or clicked between one and three months ago, but nothing in the last 30 days
- Engaged 91+ days ago or never: no engagement in three months or more
Now look at how many contacts are in each bucket. If more than 30% of your active list sits in the 91+ bucket and you're still sending broadcasts to all three groups, you're tanking your sender reputation. Mailbox providers watch engagement rates. When a large portion of your list ignores your mail, they assume the rest of the list doesn't want it either—and they start filtering.
The fix: stop sending to the 91+ group immediately. Build a re-engagement sequence for the 31–90 day group—three emails over two weeks asking if they still want to hear from you, with a clear unsubscribe path. If they don't engage, remove them. Your list will shrink. Your open rates and inbox placement will recover.
In the programs I run, I see this pattern more than any other. The list grew, the operator kept sending to everyone, engagement diluted, and Gmail started filtering. Cutting the dead weight fixes it in two to three weeks.
Review Your Recent Broadcast Subject Lines
Pull your last ten broadcast campaigns and read the subject lines out loud. Then run them through a basic spam-trigger checklist:
- All caps words (
FREE,URGENT,ACT NOW) - Excessive punctuation (
!!!,???) - Money symbols and specific dollar amounts in the subject (
$500 OFF,Make $10K) - Urgency or scarcity language that sounds like a late-night infomercial (
LAST CHANCE,Only 3 left)
If three or more of your last ten subjects hit two or more of these patterns, you've taught spam filters that your content looks like junk. Even if your list engagement is strong, content pattern-matching can drag you down.
The fix: write subject lines that sound like you're emailing a friend, not running a clearance sale. Replace "LAST CHANCE: 50% off ends tonight!!!" with "Quick heads-up: this closes at midnight." Same urgency. Doesn't trigger filters.
I'm not saying never use urgency. I'm saying don't dress it up like a 1997 spam bot wrote it. Spam filters have twenty-five years of training data. They know the patterns.
Check for Volume Spikes
Mailbox providers expect consistency. If you normally send 10,000 emails a week and suddenly send 80,000 in two days because you launched a promotion, they assume you're a spammer who bought a list.
Go into your ActiveCampaign reporting and look at your send volume over the past 30 days. If you see a sharp spike—double or triple your normal volume—that's likely the trigger. The damage is already done, but you need to ramp back down gradually. Don't go from 80,000 back to 10,000 overnight. Step it down over a week.
If you're planning a launch or a big promo, ramp volume up gradually in the week before. Send a few extra broadcasts. Increase daily send limits slowly. Give mailbox providers time to see that the spike is intentional, not a hijacked account.
The Fix Hierarchy
Once you've diagnosed the problem, fix in this order:
- Authentication issues: Fix
SPF,DKIM, andDMARCimmediately. Nothing else matters if these are broken. - High spam complaint rate: Stop sending to unengaged segments. Build a re-engagement flow and prune aggressively.
- Volume spike: Ramp down gradually and wait. If you're on a dedicated IP, you may need to warm it again.
- Content triggers: Rewrite your subject lines and remove spam-pattern language from your email copy.
Most operators try to fix content first because it feels like the easiest lever. It's not. Authentication and engagement segmentation account for 80% of reputation problems. If you fix those two and your reputation doesn't recover in three weeks, then look at content.
Your sender reputation didn't collapse because Gmail hates you. It slid because something in your program changed—volume, engagement, authentication, or content—and mailbox providers responded the way they're designed to. Run the ten-minute diagnostic. Fix in order. Your inbox placement will recover.
If you've run the diagnostic and you're still not sure what broke, I'll walk through your ActiveCampaign account and show you exactly where the problem is—no cost: https://getner.ai/audit/.