Create the DKIM DNS Record: http://www.dnswatch.info/dkim/create-dns-record Create the SPF Record: http://www.spfwizard.net/ Do not forget to add a PTR record at your provider! Verify the settings: Authentication Checker Use this command: mail -r xyz@domainthatshouldbeverified.com -s 'testerl vom roman' check-auth-myname=domain.at@verifier.port25.com< And some more information if your domain is hosting email at Google: https://support.google.com/a/answer/178723?hl=en https://support.google.com/a/answer/174124?hl=en Update 2018-01-25: Update port25 authentication checker URL