Hi jmaze, I had a similar issue with Thunderbird - My error messages were 'Connection to Server Reset' or 'Connection Refused'....

Then it seemed like one of my EMail accounts was working but not the other.

User Toad Hall on this Community site sent me a helpful response which seemed to resolve the issue but my problem seemed to be connected to my Norton 360 AV.

Suggestion was to switch off EMail protection in Norton AV Advanced Security.

I don't know if you had Norton 360 AV Installed but the Thunderbird problems started happening IMMEDIATELY after the Norton 360 recent update. Worked for me

Refer to Toad Hall post if this applies... Best wishes

Thanks Caribman. Unfortunately that's not it. No changes have been made with my virus software (I don't use email protection with it anyway).

Thanks Caribman. Unfortunately that's not it. No changes have been made with my virus software (I don't use email protection with it anyway).

You don't have to for it to mess up email. Norton blocked the new account wizard with something called Sonar that had nothing to do with email.

So what you are describing sounds like an antivirus issue that has been around for perhaps a decade, but lets try working through this.

1. Who is the mail provider? (outlook in particular is very problematic with their new oauth requirements)
2. What antivirus do you use?
3. Do you have a VPN? (They cause more email issues these days than they are worth.)
4. If you log into the account using webmail and empty the spam folder does that change anything? (corrupt emails which are usually spam can cause major issues with downloading and would be at the root of Caribman problem. Norton is notorious for just dropping the connection when it can't recognize the email layout.)
5. Is the account configured as POP or IMAP?