How to implement a DKIM signature on the server for emails sent using the PHP mail() function?

Question

Email

We have a VPS on CentOS 8 with a web server installed and mail configured accordingly (Exim + Dovecot + OpenDKIM). All mail sent through the mail client is digitally signed with DKIM and everything is fine here. But if the user sends mail using the PHP mail() function, then in this case, the letter goes already without a DKIM signature, with all the ensuing consequences.

How to implement a DKIM signature for emails sent via PHP's mail() function, exactly by means of the server (so as not to get into scripts)?

Answer 1

You need to set up a postfix\sendmail\exim mail server with DKIM that will listen on localhost and be able to send emails. The function is similar to the mail command on the server.