When email performance drops in Marketing Cloud Account Engagement (Pardot), the first instinct is always to blame the content. New subject lines get tested. Send times get debated. Someone suggests emojis.
Meanwhile, the actual problem is usually invisible: your emails aren't reaching inboxes in the first place. Deliverability — not copywriting — is the most common culprit behind declining open rates, and it degrades quietly over months until someone finally notices the trend line.
We once took over an instance where deliverability had fallen to 20% — four out of five emails never arrived — and the previous consultants had spent months A/B testing subject lines. Here's the diagnostic process we actually use.
Email authentication is table stakes, and it's been mandatory-in-practice since Gmail and Yahoo tightened bulk-sender rules. Three records matter.
SPF authorizes Account Engagement to send on behalf of your domain. DKIM cryptographically signs your emails so receivers can verify they weren't tampered with. DMARC tells receiving servers what to do with mail that fails the first two — and major inbox providers require it for bulk senders.
Check your domain status under Account Engagement's domain management settings. If anything shows unverified, stop reading and fix that first — nothing else in this post matters until authentication passes. While you're there: are you still sending from the default Pardot domain instead of your own tracker domain and sending domain? That alone suppresses inbox placement.
Open rate is a noisy metric (privacy features inflate and deflate it unpredictably). Pull the metrics that don't lie.
Bounce rate — above roughly 2% hard bounces per send signals list-quality problems that mailbox providers punish.
Spam complaint rate — even a fraction of a percent gets you throttled. Gmail's tolerance is roughly 0.1–0.3%; sustained complaints above that and you're in the spam folder domain-wide.
Delivery trends by mailbox provider. If Gmail engagement fell off a cliff while Outlook held steady, that's a sender-reputation problem at Google, not a content problem.
Sender reputation is mostly a function of who you send to. The patterns that poison it:
Sending to everyone, forever. Prospects who haven't opened anything in 18 months aren't "audience," they're risk. Mailing them tells Gmail you don't care who wants your mail.
No sunset policy. Build a dynamic list of prospects with no engagement in the last 6–12 months. Send them one honest re-engagement attempt. No response? Suppress them. Your mailable count drops; your reputation — and actual reach — rises. This trade is always worth it.
Purchased or imported mystery lists. Old imports full of dead addresses drive bounces, and spam traps live in exactly those lists.
No preference center. If the only way out is "unsubscribe or mark as spam," some people choose spam. A preference center that offers "less often" or "only these topics" converts complaints into retained subscribers.
Volume spikes. Going from 2,000 emails a week to 60,000 in one blast looks like a compromised account to mailbox providers. Ramp volume gradually, and warm up any new sending domain deliberately.
One giant monthly blast vs. steady sends. Consistent, segmented sending builds reputation; irregular mass blasts erode it.
Segmentation quality. Relevance drives engagement, and engagement drives deliverability. A well-run nurture program (this is where Engagement Studio earns its living) will outperform batch-and-blast on every metric that matters — including inbox placement.
Only after the above is clean should you look at content: misleading subject lines, link-shortener URLs, image-only emails, and broken HTML can all trip filters. But content is the tiebreaker, not the headline. Fixing your subject lines while sending to a decayed list from an unauthenticated domain is rearranging deck chairs.
Deliverability isn't a one-time fix. The instances that stay healthy do four things routinely: quarterly authentication checks (records break during DNS changes more often than you'd think), a standing sunset policy that runs automatically, bounce and complaint review after every major send, and an annual list-hygiene audit.
That last one is a standard part of our Account Engagement retainer — deliverability tuning and monitoring is listed right on the tin, because it's that consistently needed.
If your open rates have been sliding and nobody can explain why, the answer is findable. Usually within a week. Let's talk.
Founder of Thompson Technology. Salesforce and Account Engagement consultant for B2B companies.
