Zimbra Setup DKIM

Introduction

DKIM is a standard email authentication method that adds a digital signature to outgoing messages. Receiving mail servers that get messages signed with DKIM can verify messages actually came from the sender, and not someone impersonating the sender.

If your mail server is not configured with DKIM or SPF , your email will be reject sending to popular email, like a gmail

DKIM email like this, send and signing by same mail server.

Configuration

Run this command to generate DKIM

su - zimbra
/opt/zimbra/libexec/zmdkimkeyutil -a -d dosys.my.id

From the command above, it will produce output like the following

DKIM Data added to LDAP for domain dosys.my.id with selector 26CEEB0C-2486-11EE-9679-4BCDA218A4BC
Public signature to enter into DNS:
26CEEB0C-2486-11EE-9679-4BCDA218A4BC._domainkey IN      TXT     ( "v=DKIM1; k=rsa; "
          "p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAtqKR2HjopjVKU++E6dtLnITIXsvCItfEmMjC7pR2Wu5QOd+GlDJoHPwF+Hpw9NNcfuO1zsqZdCX082GMR7H6zeT3pDeo5KFpRB2Cv4rjNF/ybd9mjRBk43AeQwevuNTZ5RWJCjgP0OWecF9+9srEn56QBJ21dXd3yV/UJfojYnIkjth9WOIHAk1K4vxto9QLseUpXjsRohs8r0"
          "N8wK+Sg7zYCiw/Tuqcc+UBGCgbcaLJD2O8PJor5GcwGE/6fV4yFXFzme+qHK6aU8Hn2x+ERotF8LRSAI6c3RgUBAwnPsmg0vBCyshkumHIKfaN33aB+DxjBsax5ovNRNWGFZ8epQIDAQAB" )  ; ----- DKIM key 26CEEB0C-2486-11EE-9679-4BCDA218A4BC for dosys.my.id

Selector:

26CEEB0C-2486-11EE-9679-4BCDA218A4BC._domainkey

Content using DKIM Record:

v=DKIM1;k=rsa;p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAtqKR2HjopjVKU++E6dtLnITIXsvCItfEmMjC7pR2Wu5QOd+GlDJoHPwF+Hpw9NNcfuO1zsqZdCX082GMR7H6zeT3pDeo5KFpRB2Cv4rjNF/ybd9mjRBk43AeQwevuNTZ5RWJCjgP0OWecF9+9srEn56QBJ21dXd3yV/UJfojYnIkjth9WOIHAk1K4vxto9QLseUpXjsRohs8r0N8wK+Sg7zYCiw/Tuqcc+UBGCgbcaLJD2O8PJor5GcwGE/6fV4yFXFzme+qHK6aU8Hn2x+ERotF8LRSAI6c3RgUBAwnPsmg0vBCyshkumHIKfaN33aB+DxjBsax5ovNRNWGFZ8epQIDAQBE

Add to DNS Server, with TXT record

If you're using PowerGSLB, maximum character in record is 255, We have to increase the character by update the columns database

Read Here

example record in PowerGSLB:

26CEEB0C-2486-11EE-9679-4BCDA218A4BC._domainkey.dosys.my.id

Content using DKIM Record

Testing

Access Mail-Tester, send email to mail-tester email

After send it, click check your score

Make sure your DKIM signature is valid