Receiving but can not send

I finally seem to have my account working. It just point blank refused to connect until this morning…no matter what combination of account settings.
I can receive mail but can not send mail.
Under eM account settings, and the pop tag there is only one server…stmp.
However on my server there is a pop for receiving and a stmp for sending.

How do I correct??

Many thanks for reading.

Hi, can you make screenshot of your Tools - accounts - your account - smtp tab? And what email service provider do you use?