Emails going to spam after server migration and new IP address

Question

I just migrated my web server to a new host, which came with a fresh IP address. Now, all of a sudden, my application's notification emails are getting flagged as spam. I've checked the obvious things like ensuring SPF is set up correctly for the new IP in my DNS. The IP isn't on any blacklists I can find. What are the most common reasons for this happening with a new IP, and what steps should I take to build its reputation?

admin · Accepted Answer

The most common reason is a poor sender reputation on the new IP address, which is treated as unknown and untrusted by recipient filters. IP reputation is built over time through consistent, legitimate sending patterns. A sudden shift from zero volume to your application's full volume appears suspicious. Furthermore, technical authentication like SPF alone is insufficient; you must also implement DKIM and DMARC, and ensure your server's reverse DNS (rDNS) is correctly configured.

First, verify all critical DNS records using dig or nslookup commands. dig TXT yourdomain.com
nslookup -type=ptr your.server.ip.address Check that the rDNS matches your server's hostname and the domain you send from. Next, implement DKIM signing for your emails and publish the public key in DNS, then add a DMARC policy to instruct receivers how to handle failures. v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com

To build reputation, start by sending low volumes of non-critical emails to engaged users for several weeks. This warm-up period signals to mailbox providers that the IP is used for legitimate traffic. Monitor delivery metrics and authentication reports from your DMARC aggregate feed to identify any issues early.

Emails going to spam after server migration and new IP address

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