Do you mean you cannot send anything from your officepoint email address ? Or do you mean you can send generally but not to the particular hotmail email address ?

I notice you have a company signature... Do a test - click on 'Write' or 'New Message' Remove all the signature compose a simple email and send to an email addess you can check. This will tell you if issue is with the signature.

In Thunderbird Help > TRoubleshooting Information Scroll down to 'Mail and News Accounts' Copy all the data and paste info into this forum question.

Then we can check what you are using for the SMTP settings?

In the meantime, I suggest you check to see if your email addess and also your IP address has been put on some spam list. See if spamhaus has some info. https://check.spamhaus.org/

Hello - is everything ok? What did you discover was wrong ?