I've generated private key and public key using following commands.

openssl genrsa -des3 -out server.key openssl rsa -in server.key -out server.key.insecure

mv server.key server.key.secure mv server.key.insecure server.key

openssl req -new -key server.key -out server.csr

openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

it shows error message while verifying for DKIM that public key(server.crt) should not be longer than 512 character.

closed as unclear what you're asking by TomTom, mdpc, kasperd, MadHatter, Ward Feb 5 '16 at 5:21

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • You may also wish to read our canonical question on SPF configuration. – MadHatter Jan 26 '16 at 13:59
  • You really have a shotgun approach to tagging. Adding tons of irrelevant ones. Oh, and btw - where does SPF appear, outside the tag and title? Because the question is not about SPF but DKIM. – TomTom Jan 26 '16 at 14:30

SPF doesn't use certificates, so you have misunderstood mechanisms used by SPF to stop the use of forged "from" addresses.

SPF is based on set a DNS TXT record in which you specify simple policies of what hosts can send mails using your domain name like this:

v=spf1 mx a:pluto.example.net include:aspmx.googlemail.com -all

You are probably confused with DKIM.

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