My Late 2013 mojave 10.14.6 will not send emails. It comes up with the message 9Cannot send message using this server. I've had the isp people look at it 3 times and they say it's a mac problem. Can anyone help? Thanks
Rule No. 1 it is always a Mac problem never an ISP problem ( in other words they do not understand Macs ).
Try opening Mail Preferences > General > Accounts and clear the fields and then re-submit. There are some ISP's down under that are Mac specialists such as Internode and Aussie Broadband.
Try connecting (sending/receiving) to the server using OTHER email clients.
Some examples:
- Thunderbird
- GyazMail
- Try a web-based interface if the server offers one
If NONE of these will connect, it could be at the server end.
If ONE or more DOES connect, take careful note of all the send/receive settings. Then try to "transfer over" these settings to Mail.app.