I have a few VPSs (all of them uses the same OS) and they all have the same Virtualmin+Webmin versions installed. The Webmin and Virtualmin settings too are the same on all of them.
For some weird reason, one of the servers can’t connect to external SMTP servers even though I’ve checked and confirmed that the Postfix and Dovecot settings are set up in the same way as on the other servers.
I have a dummy WordPress site on the server that I have configured to send mail via SMTP (manually setting SMTP up by configuring wp_mail as well as using an SMTP plugin) but test mails sent from the site are not delivered.
However, when I do the same thing (using wp_mail or SMTP plugin) on live WordPress sites hosted on the other servers, the test mails are delivered without a problem.
Running “re-checking configuration” returns no errors and I tried checking the mail logs in /var/log/mail.log but there isn’t anything useful there too other than a few lines about brute-force login attempts (SASL LOGIN authentication failed).
What could be causing this particular server to be unable to connect to external SMTP servers?
@Gomez_Adams That is the same SMTP plugin that I used on the other servers as well as the one I tried on this server lol The server as well as the WordPress sites on it can’t connect to external SMTP servers (self-hosted mailservers or providers like Google, SendGrid, Sendinblue etc) even though the Postfix configuration is exactly the same as on the other Virtualmin+Webmin servers that I have with SMTP working.
System notifications from Webmin for example, are not getting delivered when I try to send them via SMTP either.
And my mail.log doesn’t show anything related to this SMTP issue other than lines about failed login attempts by bots every now and then.
That may be the problem. I think that plugin is limited if it’s not the pro version. If they see multiple instances running that plugin through the same IP I think they limit it unless you upgrade to the pro version.