A few weeks ago I posted that I've been experience a lower than usual open rate falling from around 42% to 29%. Someone suggested I look into Google Postmaster for information on spam rate and deliverability. I got this to work and started investigating but can't determine what I should do. I provided information below. Thanks! Edit: It is important to note that I use the same template and sending method (a data extension for every monthly send so nothing has changed here)
Deliverability analysis:
"A significant percentage of your messages have delivery errors, typically a result in sudden increase in sending volume or issues with your infrastructure. The errors are causing a delivery delay for the affected messages."
Recommended action: Check the STMP logs for your outgoing email. Reduce sending rate and check the SMTP bounce message for more details and instructions.
Delivery Errors for recent sends
Error type: reject, reason: suspected spam, percentage: 7.32%
Error type: reject, reason: suspected spam, percentage: 71.53%
Error type: reject, reason: suspected spam, percentage: 0.69%
Spam rate:
July: 0.04%
August: 0.08%
September: 0.03%
I was also told to run it through Senderscore for my IP address and it came back with a high score of around 90 so it shouldnt be the IP address.
Hi Taylor,
Two different signals here: Spam Rate (0.03–0.08%) = user complaints on delivered mail — that's fine. "Suspected spam" delivery errors (71.53%!) = Gmail rejecting/deferring mail at SMTP before it's even delivered. That's your open-rate drop right there — rejected mail can't be opened.
Since template/process are unchanged, likely causes:
1. List engagement decay — reusing the same DE monthly means unengaged/dead Gmail addresses pile up over time. Gmail's filtering is engagement-based, so this alone can trigger a spike even with zero content change. Prune addresses with no opens/clicks in the last 3–6 sends.
2. Auth drift — SPF/DKIM/DMARC can silently break (DNS changes, key rotation, lookup limits) without touching the email. Check a recent header via Google's Messageheader tool.
3. Check Postmaster's own Domain/IP reputation graphs (not SenderScore — different data source) for a Gmail-specific drop to Medium/Low.
4. Tracked/redirect links in the template can carry their own reputation issues independent of content — test them via Google Safe Browsing/VirusTotal.
Start with #1, it's the most common cause of this exact pattern.
Reference:
https://support.google.com/mail/answer/9981691
