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Transactional mail via Mailgun/Postmark/SendGrid lands poorly, DKIM and SPF unclear

For solid delivery the sender (Mailgun/Postmark/SendGrid) must DKIM-sign for your domain, not theirs. That requires your own DKIM selector via CNAME or TXT in your zone, plus an SPF include or DKIM-only alignment in DMARC.

Try this first

  1. 1In the sender portal, create a sending domain for your own domain (mail.vectel.nl or vectel.nl), not their default.
  2. 2Place the supplied CNAME records (Mailgun uses smtp._domainkey, Postmark pm._domainkey, SendGrid s1._domainkey and s2._domainkey) in your DNS.
  3. 3Add the SPF include to your apex SPF (include:mailgun.org, include:spf.mtasv.net, include:sendgrid.net), watch the 10-lookup limit.
  4. 4Only enable sending in the portal once DNS resolves, otherwise their default domain signs and DMARC alignment breaks.
  5. 5Test with mail-tester.com from a test account, expect 10/10 with SPF, DKIM and DMARC all green.

When to bring us in

If you have many transactional senders and SPF gets long or DKIM messy, we can sort which vendor stays and which can run via a single relay.

See also

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