Everything I've read points to ATT/Verizon/AOL/Yahoo or whatever they are known as these days. See: http://kb.mozillazine.org/Yahoo#The_POP3_email_server_.28plus.pop.mail.yahoo.com.29_does_not_support_UIDL_or_XTND_or_XLST and https://support.mozilla.org/en-US/questions/1238352 https://support.mozilla.org/en-US/questions/1221957

I strongly recommend using IMAP instead.

The POP3 mail server (pop.bizmail.yahoo.com) does not support UIDL or XTND XLST, which are required to implement the ``Leave on Server,

2 Apr 20 I have been doing a LOT of research in to this problem. Problem started for me around Oct/Nov 2019 I rebuilt TBird and new profiles in January 2020 Same issue I run two business accounts in Thunderbird, and one free account.

My Business and free accounts are with yahoo, and have been for more than 10 years. i have been running TBird for about 10 years also.

The Business accounts both download messages ( Win 7 64 ) initially and then over a course of a day cease downloading new messages. Thunderbird does not fail downloading messages from my free Yahoo account, only the business ones.

Using Linux openssl and running the command

s_client -connect pop.bizmail.yahoo.com:995 I can list email in my business accounts, read emails no problem using LIST, TOP etc so the mail is there, accessible.

I don't have a network /  authentication problem and my free Yahoo account is still accessible using TBird.

If I email myself from a business account and cc my Yahoo free account, Tbird will pick up the mail in my free account and report the error ( above ) when i try to manually get messages from my business accounts.

Frustratingly, this error is NOT shown when TBird is just auto updating, so you can sit for hours and get no mail, and no warning, that Bird has failed to update.

You only get the error if you manually click Get Messages

Stans said

Everything I've read points to ATT/Verizon/AOL/Yahoo or whatever they are known as these days. See: http://kb.mozillazine.org/Yahoo#The_POP3_email_server_.28plus.pop.mail.yahoo.com.29_does_not_support_UIDL_or_XTND_or_XLST and https://support.mozilla.org/en-US/questions/1238352 https://support.mozilla.org/en-US/questions/1221957

Is it your pop.bizmail.yahoo.com or pop.mail.yahoo.com that is timing out? My Business mail is the one I have issues with pop.bizmail pop.mail.yahoo.com does not time out or throw the error when i click Get messages

I CAN read messages in the command line to check the mail servcer is accessible using Linux / Openssl / s_client -connect pop.bizmail.yahoo.com:995 user pass

etc

Since restarting Thunderbird seems to at least temporarily fix the problem, it seems to me that, independent of what strange things the mail server is doing, Thunderbird should restart itself (or do whatever the equivalent is internally) when it receives this error from the server. And in any case, it shouldn't silently ignore the error, but rather alert the user without the user having to manually attempt to get new messages.

_ms_ said

Thunderbird should restart itself (or do whatever the equivalent is internally) when it receives this error from the server. it shouldn't silently ignore the error, but rather alert the user without the user having to manually attempt to get new messages.

Agree completely I have sat and seen no incoming mail, then rebooted TBird to see them all come in. TBird must know there is an issue but only reports it when you manually click Get Messages

Update 3 April 2020 I built a brand new Ubuntu 18.04  : fully updated Identical behaviour on Thunderbird when linked to pop.bizmail.yahoo.com Ironically with my Windows machine and Ubuntu machine running in parallel, it was the linux machine to stop loading emails first.

Using openssl s_client -connect pop.bizmail.yahoo.com:995 user foobar pass foobar list then top NumberOfLastEmail NumberOfLinesToDhow eg : top 560 10

I could read my emails just fine

What is TBird doing ( in Linux and Win64 ) that is causing emails to be unable to be accessed without a reboot of the client?

What is 'counting up' or accumulating so that after a period of activity TBird stops accessing certain servers ? As noted before my TBird does not seem to fail on pop.mail.yahoo.com

It is this last piece of information that makes me question is this TBird or my provider and differing actions of servers?