Hello & Welcome to JustAnswer. I'm Kamil and i will do my best to assist you.
I think the issue is related to settings, would you like me to remotely connect to your computer to troubleshoot the issue? Thunderbird is also an e-mail client, i believe if the settings on it or outlook are correct then both should work.
The send and receive work but as I have said " when I try to send an email it will not go". Receiving emails works perfectly. As a matter of interest the settings were gone through with a technician from my provider yesterday and it made NO difference.
May i remotely connect to check? I am positive that i will be able to fix the problem, if not then set you up on Thunderbird.
Please click the link below and run the downloaded program