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Dev.to
7/4/2026
Running a mail server on a VPS: what actually keeps you out of spam

Running a mail server on a VPS: what actually keeps you out of spam

Short summary

Mail server deliverability depends on three DNS records (PTR for reverse lookup validation, SPF and DKIM for sender authentication, DMARC for policy enforcement), a dedicated IP address, and host permission to use outbound port 25. Most delivery failures trace to a missing or mismatched PTR record, which receiving servers check immediately when your mail arrives. Configure all three DNS records, request port 25 access from your host, then test with mail-tester.com to verify nothing is falling into spam folders.

  • •PTR (reverse DNS) must match your mail hostname; receiving servers check this before accepting mail
  • •SPF, DKIM, and DMARC together verify you own the sending domain and set handling policy
  • •Dedicated IP and open port 25 are prerequisites; shared IPs inherit prior tenant reputation

Generated with AI, which can make mistakes.

#open-source
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