Thunderbird email not connecting on a specific computer

Question

Turned on my computer this morning and none of my emails connect on Thunderbird. All of them give the message: "server email@email has disconnected. The server may have gone down or there may be a network problem"

I run Thunderbird (same version) on my laptop and it can connect to the emails fine on that. They can also connect fine on my phone, so it's definitely specific to my PC. Here's what I've tried so far:

• Disabled Firewall / anti-virus (eset)
• Cleared cache on thunderbird
• Registry clean and cache clean (ccleaner)
• System restore to before last windows update (there was one this morning so I thought it may have been that)
• Uninstalled / reinstalled thunderbird
• Restarted router
• Disabled Thunderbird addons

No idea why this has started happening and nothing seems to fix it! not sure what else I could try. Any suggestions?

Answer 1

OK I fixed it if anyone else has this issue. This is what I did:

ESET Smart Secuirty was the issue. Even though I had disabled protection (both firewall and antivirus) when troubleshooting, it didn't stop ESET scanning my IMAP connections which is what was causing the issue.

To fix this you go to the ESET Smart Security Advanced setup -> Web and Email -> Email client protection -> IMAP, IMAPS -> untick 'enable IMAP checking'.

Answer 2

Alternate cause and solution could be the maximum number of connections to be cached, which was the case for me:

Go to menu Tools > Account Settings > Server Settings > Advanced... and reduce the value for Maximum number of server connections to cache until the message does not occur anymore after switching folders or checking mails (which was "2" in my case).

Answer 3

Fought this problem for hours until I ran netsh winsock reset from the command line. Problem gone!