How would you troubleshoot a sudden drop in email deliverability?

First I establish what actually dropped — delivery rate, open rate, or both — and whether it is universal or concentrated at particular mailbox providers. A drop at one provider points to a reputation or filtering issue there; a drop everywhere points to authentication or list quality.

Then I check the mechanics: are SPF, DKIM, and DMARC still aligned for the sending domain? Did anyone change DNS, add a new sending tool on the same domain, or switch the from-address? Has bounce volume risen, which would suggest a stale or purchased list entered the database?

I look at recent sending behaviour: a sudden volume spike, a send to a long-dormant segment, or a new IP without a warm-up plan will all trigger filtering. I check spam complaint rates and whether the unsubscribe path is easy to find — people who cannot unsubscribe report as spam instead.

Remediation is usually the same shape: stop sending to unengaged segments, tighten to recently engaged prospects to rebuild reputation, fix authentication, and reintroduce volume gradually.