SPF errors when sending emails

Branislav B. asked:

I setup a mail server on mail.mydomain.com. I am able to receive email. Problem occurs when i try to send an email. I have two servers:

  • mail.mydomain.com – which is on different ip (e.g.
  • mydomain.com – which has also different ip (

My SPF record says:
v=spf1 mx ip4: -all

My mx record for mydomain.com points to mail.mydomain.com

When i try to send an email I’m getting following error:

From google:

gmail-smtp-in.l.google.com[2a00:1450:400c:c06::1b] said: 550-5.7.1
[2001:bc8:4400:2b00::32:1f 12] Our system has detected that this
550-5.7.1 message is likely unsolicited mail. To reduce the amount of spam
sent 550-5.7.1 to Gmail, this message has been blocked. Please visit
550-5.7.1 https://support.google.com/mail/?p=UnsolicitedMessageError 550
5.7.1 for more information. m21si1136366wml.110 – gsmtp (in reply to end
of DATA command)

From other server:

host mx1.seznam.cz[2a02:598:2::42] said: 550 5.7.1
Sender Policy Framework of `futeq.com’ domain denied your IP address. (in
reply to MAIL FROM command)

For gmail I also registered and verified my domain using postmaster.google.com

Can anyone point me to the right direction? am I missing something ?

PS: I checked and my IP is not blacklisted


My answer:

It looks like you forgot to add your IPv6 address to your SPF record, and quite possibly to your DNS AAAA record for the sending host.

Of course, mx in the SPF record covers all IP addresses of the host named in the MX record, so naming the same IP addresses in the SPF record is redundant.

To fix the problem, add your IPv6 address in the DNS AAAA record for your host.

View the full question and any other answers on Server Fault.

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