MX records
Senders try the mail server with the lowest priority number first, falling back to higher numbers. A single MX of 0 with a target of . (null MX, RFC 7505) means the domain never receives mail.
Protecting the domain
DKIM keys sit under a selector name only the sender knows, so they cannot be listed without it.
- SPF lists the servers allowed to send as the domain. Exactly one record; end it with -all or ~all.
- DMARC tells receivers what to do when mail fails SPF and DKIM alignment, and where to send reports. Start with p=none, then move to quarantine or reject.
- MTA-STS and TLS-RPT require encrypted delivery to your servers and report problems.
Questions
- Why are my emails going to spam?
- Common causes: no SPF or DMARC, a sending server without matching reverse DNS, or a sending address on a blocklist. Check all three here and on the blacklist checker.