Emails are not signed with DKIM in case they are sent using
mail()PHP function or mail utility, below information can be found in
dk_sign: Starting the dk_sign filter...
dk_sign: DKIM error: DKIM Feed: Syntax error
plesk sendmail: Error during 'dd51-domainkeys' handler
postfix/pickup: 024B213A0AE6: uid=10000 from=<[email protected]>
check-quota: cannot get sender domain
check-quota: Unable to intialize check-quota mail handler
plesk sendmail: Error during 'check-quota' handler
postfix/pickup: 04655870621: uid=10000 from=<[email protected]>
As a result mail is delivered to spam folder
This is Plesk bug with ID PPPM-6690 which is planned to be fixed in future product updates.
As a workaround, specify email headers manually or submit a message directly through SMTP server. One of the following PHP scripts can be used as an example: