An option that worked for me was to set up outgoing mail as IMAP. (Most if not all providers do not like mail sent through their systems from outside the service.
Start the process to set up outgoing mail.
Fill in log in and passwords
Mail setting is IMAP
Security is SSL
Outgoing mail server could be anything. mine is mobile.charter.net It could be outgoing.xxx.xxx or imap.xxx.xxx or any server name you already use. So you will have to try different settings
Port number is 993
When it tests if it is set upcorrectly you will know. If not, I would keep changing the outgoing server name and keep everything else the same
I did also try iMap and it would not work. Get this though, over the weekend I received an update that was pushed out and now my email is working.
The update was supposed to salve a problem for exchange users, but my POP3 account is mysteriously working now....
Thanks for replying to my post.
If nothing else works use Gmail.
You can use their smtp.gmail.com and if you setup your gmail account settings, on the web site, under settings - accounts and import - select send mail from other addresses, follow the prompt to add your mail account - and then select always send messages from the account that they were received from.
And you should be good. I had to do this with my college email for both thunderbird and my android.