Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_how-to-find-your-profile

I found the Thunderbird profile and added it to Defender's scan exclusion but outgoing messages still get timed out.

Please post your Troubleshooting Information. At the top right of the Thunderbird window, click the menu button ≡, then select Help > More Troubleshooting Information. Press the "Copy text to clipboard button" and paste the information into your reply.

Thank you for your suggestion, but the problem seemed to be in the Outgoing Server settings in Thunderbird. I changed Connection Security setting to "STARTLS" I changed Auth Method to "No Authentication"

I don't know which (or both) was the solution, but I am no longer getting timed out when sending email.

Well no authentication should mean you can not send mail at all. Your providers settings here state

SSL: On (which translates to SSL/TLS in thunderbird in settings.) Outgoing Port: 587 Requires Authentication: Yes, or checked (which translates to "normal password" in Thunderbird)

So according to your mail provider your outgoing mail should not work using those settings.

I am just wondering why you are creating exceptions in Defender when you are using Norton. I will not go into it, but I personally consider Norton to be akin to the viruses they claim to protect against. Fundamentally stopping Norton does not do as advertised. You have to uninstall it to actually get a Norton free result, or run the operating system in safe mode with networking. With the operating system in safe mode with networking you can actually feel you have disabled Norton. However as internet in safe mode requires a wired connection many folks these days can not actually utilize this test to determine if their antivirus is the problem.

Thanks for your comments. I wasn't clear earlier, I UNISTALLED Norton (didn't just turn it off) before setting up the exception in Defender. Long story why I was temporarily using Norton, but I agree with your view on it and I am back to just using Defender.

Not sure why Thunderbird outgoing email is working with these settings, but I'm going to leave it alone for now. I'll save your note and link in case I have issues down the road.

Thanks!