Ignore POP settings in $bounce_mailbox_port

[lwcorp]

Since it works only with IMAP, and thus require a manual change in config.php, consider replacing the word pop3 with imap`, port 995 with 993, etc.

You can then log it in the output whether it fails or not, so the user will know their real setting was ignored. This will spare the need for any manual changes, especially given this plugin might have to come as default.

[bramley]

I have applied your suggestions. There might still be a need to change config.php because $bounce_mailbox_host might differ between POP3 and IMAP, gmail does that for example https://developers.google.com/gmail/imap/imap-smtp#protocol . I have added that to the documentation.

[lwcorp]

Works, thanks! Since Gmail is so popular, should you feel free replacing ^pop(\.gmail\.com)$ to imap$1 on your own? What do you think?

For other servers, do you think it should be a feature request for phplist to divide $bounce_mailbox_host into $bounce_mailbox_host_pop3 and$bounce_mailbox_host_imap? with either of them could be commented out if not needed?