This may be known to some or many, but to help others who have this prob but have followed the instructions and can't understand why it doesn't work......
Mail > Preferences > Accounts > Outgoing Mail Server (SMTP) (click on chosen server > Edit SMTP Server List > Advanced > Change to 'Use Custom Port' and add port number required.
On my Mac, it was fine immediately.
Best
Paul
Mail > Preferences > Accounts > Outgoing Mail Server (SMTP) (click on chosen server > Edit SMTP Server List > Advanced > Change to 'Use Custom Port' and add port number required.
On my Mac, it was fine immediately.
Best
Paul