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Hey, it's Pavel. Email Deliverability Expert helping email operators raise the bar for themselves and their teams. I'm building this newsletter for high-performing email marketers who want to stay ahead of the game. If you're serious about email deliverability, don't forget to subscribe.
When Multiple ESPs Break Your Email Delivery
You do everything by the book. New app, new domain, Mailgun connected, tests pass, developers see every email. Then you launch, real users arrive, and suddenly email stops behaving.
That is what happened with a client I worked with recently.
They had a small product app with a weekly re-engagement email that worked perfectly during beta. Once the user base passed one thousand people, that same campaign stopped reaching most inboxes.
Roughly 30% of users received the email. The other 70% saw nothing.
SPF and DKIM were configured. Mailgun was in place. Dashboards looked fine. Yet Gmail and Outlook were either rejecting messages or dropping them into spam.
This is what real-world authentication failure looks like.