The email service can be used normally, but the dkim signature part is still missing. Refer to multiple guides, such as the two below.
https://blog.csdn.net/yetugeng/article/details/83996397 (Chinese website)
https://forum.virtualmin.com/t/dkim-setup-failed/117124/2 (Japanese website)
The error is reported as a configuration problem.
Aug 8 14:27:19 saikano postfix/smtpd[105588]: warning: connect to Milter service inet:127.0.0.1:8891: Connection refused
Aug 08 15:29:23 saikano.top systemd[1]: opendkim.service: Main process exited, code=exited, status=78/CONFIG
Aug 08 15:29:23 saikano.top systemd[1]: opendkim.service: Failed with result 'exit-code'.
Aug 08 15:29:23 saikano.top systemd[1]: opendkim.service: Scheduled restart job, restart counter is at 5.
Aug 08 15:29:23 saikano.top systemd[1]: Stopped DomainKeys Identified Mail (DKIM) Milter.
Aug 08 15:29:23 saikano.top systemd[1]: opendkim.service: Start request repeated too quickly.
Aug 08 15:29:23 saikano.top systemd[1]: opendkim.service: Failed with result 'exit-code'.
Aug 08 15:29:23 saikano.top systemd[1]: Failed to start DomainKeys Identified Mail (DKIM) Milter.
Reconfigured a few times and looked for similar issues.
https://forum.virtualmin.com/t/dkim-setup-failed/117124
Try to find out the problem according to the answer, but the result is unexpected. No such file or directory.
Use journalctl to find problem. journalctl -u opendkim.service
Aug 08 13:55:41 saikano.top systemd[1]: opendkim.service: Failed with result 'exit-code'.
Aug 08 13:55:41 saikano.top systemd[1]: opendkim.service: Scheduled restart job, restart counter is at 3.
Aug 08 13:55:41 saikano.top systemd[1]: Stopped DomainKeys Identified Mail (DKIM) Milter.
Aug 08 13:55:41 saikano.top systemd[1]: Started DomainKeys Identified Mail (DKIM) Milter.
Aug 08 13:55:41 saikano.top opendkim[103885]: /etc/opendkim/keys/default.private: open(): No such file or directory
Aug 08 13:55:41 saikano.top opendkim[103885]: opendkim: /etc/opendkim.conf: /etc/opendkim/keys/default.private: open(): No such file or directory
Aug 08 13:55:41 saikano.top systemd[1]: opendkim.service: Main process exited, code=exited, status=78/CONFIG
But the file is here, this is completely different from these two questions!
