I can't find a similar thread to this.
Up until about 4 days ago my email was working fine.
Then I couldn't retrieve email.
I checked the mailboxes and there is recent mail in them, so it is receiving fine, and putting the mail in the correct boxes.
When I try to retrieve the email with a client it logs in OK, but doesn't get any email.
When I try https://mydomain:81/mailuser
I get a "can't connect error" (same with webmail) however I am able to log in to ISPConfig as admin on port 81.
I have run Postfix check and get no errors.