Had to move to a new laptop. Had the same version of Thunderbird installed on both (older than v60), and just copied the Profile directory over. At that time, two of the four accounts would work, the other two would get stuck on showing a message in the status bar that read: "<account email> Connected to: <server name>" And then, nothing. I figured it was something odd, so I uninstalled that version of TB, and installed the latest. Set up first email account - one that '''worked''' on the old version - and it now freezes the same as the other accounts on the old installation. (When uninstalling the old version, I DID remove both Thunderbird profiles in Roaming and Local AppData directories. Got some logs using the log settings: `IMAP:5,LDAP:5,Mailbox:5,MailDirStore:5,MsgBiff:5,timestamp` And the log is here: https://pastebin.com/V83aiSga Essentially, it seems that it tries to connect, then immediately disconnect or give up. Specifically: 2020-10-29 00:01:54.610000 UTC - [(null) 24192: IMAP]: I/IMAP 20012000:mail.server.com:NA:ProcessCurrentURL: entering 2020-10-29 00:01:54.610000 UTC - [(null) 24192: IMAP]: I/IMAP 20012000:mail.server.com:NA:ProcessCurrentURL:imap://mike%40server%[email protected]:143/select%3E%5EINBOX: = currentUrl 2020-10-29 00:01:54.874000 UTC - [(null) 24192: IMAP]: D/IMAP ReadNextLine [rv=0x805a3ff2 stream=1FD35AC0 nb=0 needmore=1] 2020-10-29 00:01:54.875000 UTC - [(null) 24192: IMAP]: I/IMAP 20012000:mail.server.com:NA:CreateNewLineFromSocket: clearing IMAP_CONNECTION_IS_OPEN - rv = 805a3ff2 2020-10-29 00:01:54.875000 UTC - [(null) 24192: IMAP]: I/IMAP 20012000:mail.server.com:NA:TellThreadToDie: close socket connection Any pointers appreciated! -Mike