Hey everyone,
I’ve been running our email program through Mailchimp for about three years now, serving a B2B SaaS audience with a list of around 85,000 contacts. Our typical send volume is 2-3 campaigns per week, plus automated nurture streams. Historically, our deliverability stats have been solid, with inbox placement rates consistently in the high 90s.
Over the last 4-6 weeks, however, I’ve noticed a worrying and steady decline. Our open rates have dropped by nearly 30% across the board, and we’re seeing more hard bounces than usual from previously valid addresses. I’ve also had a handful of subscribers (who I know personally!) mention important transactional emails landing in spam, which is a huge red flag.
I’ve done all the standard troubleshooting steps:
* Re-verified our domain authentication (DKIM, SPF, DMARC) and it’s all set up correctly.
* Checked blacklists consistently – we’re not listed anywhere.
* Segmented out our most engaged users and sent a test campaign to them specifically – even that saw a 15% lower open rate than the historical benchmark for that segment.
* Our complaint rate is negligible (<0.1%), and we have a consistent send pattern.
This makes me wonder if something has shifted on Mailchimp’s end, or with their shared IP pools. We’re on a Pro plan but not a dedicated IP, as our volume hasn’t justified it. Our business model is mid-market SaaS with moderate traffic, so we’re not sending millions per month.
I’m curious if others in similar situations are seeing this:
* Are you on a shared IP plan or dedicated?
* Have you noticed a decline specific to certain mailbox providers (Gmail/Workspace, Outlook, etc.)?
* Did any specific remediation steps actually move the needle for you?
I’m starting to feel like this might push us toward evaluating a more robust platform like HubSpot or a SendGrid for greater control and transparency. The lack of clear insight into root causes is the most frustrating part!
— Emma
If it's not measurable, it's not marketing.
Ugh, that's a tough spot to be in. Especially when you've done the foundational work and your complaint rate is that low. It sounds like you're hitting more than just a standard sender reputation hiccup.
Have you looked at your content patterns? ESPs are getting really sensitive to template and copy similarity lately. If you're sending 2-3 campaigns a week with similar structures, it might be tripping new "bulk" or "generic" content filters that you wouldn't see on blacklists.
I had a similar scare with a different ESP recently, and switching up our subject line format and image-to-text ratio for a few sends seemed to reset something. It's worth testing a campaign that feels genuinely different.
Switching templates feels like treating the symptom, not the disease. If an ESP's filters are that brittle, they're a black box failure point. My money's on network-level reputation shifts they aren't disclosing.
Content tweaks might get you a temporary bump, but you're just dancing on their platform. Seen this before with shared IP pools.
Your vendor is not your friend.
That's a significant drop, especially on a high-value B2B list where engagement is usually stronger. You've covered the major technical checks.
You mentioned that even a segmented campaign to your most engaged users underperformed. That points to a potential issue beyond just list health or content. When that happens, it often suggests a sender reputation problem tied to your specific sending infrastructure, not just subscriber behavior.
Have you considered the impact of your automated nurture streams in this analysis? A change in their performance could be dragging down the overall sender score for your domain or dedicated IP. It might be worth isolating the stats for those transactional and triggered emails over the same timeframe.
That's a really sharp point about the automated streams. Even a small drop in engagement on a high-volume automated series can pull down your aggregate metrics in a way a few campaigns won't. It's easy to focus on the campaigns you actively launch and miss the silent workhorses.
I'd add that it's worth checking if there's been any change in complaint handling for those automated emails. Sometimes a tweak in a confirmation or reminder email can unintentionally trigger more "report spam" actions, which hits reputation hard. A quick look at the feedback loop stats for just those streams could be revealing.
Keep it civil, keep it real.
That's a lot of solid checks, kudos. When you say you have a consistent send pattern, are you using the exact same time/day for every campaign? I heard some ESPs might flag overly predictable schedules as potential automation spam, even for legit senders. Could mixing up your send times a bit help?