On the original Computer is it showing this update as available or having already having been applied? What OS is on the respective computers. Does saving/backing up your Thunderbird settings and updating / reinstalling the application fix the issue?

I don't know how to manually update. When I click on help/about thunderbird it doesn't seem to do anything.

Both computers are running windows 7 pro. The original computer is running the 64 bit windows and the other one is 32 bit.

I guess I could try removing the account and then re-installing it

I enabled the use of less secure apps at the yahoo web mail site. Yahoo seems to treat thunderbird as if it's a less secure app. None of my other yahoo mail accounts have this problem (so far).

The original computer doesn't show any updates available. I don't know how to check if it was applied.

I removed the old account (after backing it up) and reinstalled it and now it's able to connect.

It's back to not connecting again.

cisz said

I don't know how to manually update. When I click on help/about thunderbird it doesn't seem to do anything.

It should show a Check for Updates button. If clicking that doesn’t do anything, try disabling "Use a background service to install updates" in the Updates section of the Options > Advanced tab beforehand. Also, what version is installed there, and what version does the other system run?

I guess I could try removing the account and then re-installing it

So you did, but it shouldn’t be necessary, also because that will restore some prefs, or not remove old ones.

I enabled the use of less secure apps at the yahoo web mail site. Yahoo seems to treat thunderbird as if it's a less secure app. None of my other yahoo mail accounts have this problem (so far).

Are the other accounts set up in the same Thunderbird on that computer?

The original computer doesn't show any updates available. I don't know how to check if it was applied.

The Update tab shows a Show Update History button. What does it say?

I’m not familiar with any recent TB updates that would address Yahoo login issues. Also, since the issue seems to be account specific if I get that right, double-check the Account settings (server/ports/authentication method) to make sure they’re identical. On the other hand, issues with POP servers at Yahoo aren’t very rare and you didn’t change anything at your end, so this may not be Thunderbird’s fault.

There have been similar reports like these that were solved by changing the Yahoo account password using your web browser, so perhaps you should try that first. See this support question, and the other one mentioned there for more info.

Ok - so far it seems like the problem is that I unchecked the box to delete messages every 14 days while leaving the box checked "until I delete them". When I looked at an account that wasn't having problems getting messages, I saw that both boxes were checked. (I assume that it doessn't make sense to say I want the messages deleted every 14 days at the same time as saying I don't want them deleted until I delete them.)

Anyway, when I unchecked the "14 day" box on the account that had been functioning, it started having the same problem as the other one.

Also, Yahoo says that imap is not secure and wants people to use pop instead. But with pop, you don't get "sent mail", or "junk" folders.

Also, I'm still getting the error about "sending of password did not succeed".

I had changed the password at the webmail site yesterday.

Also, I don't see an update tab.

cisz said

Ok - so far it seems like the problem is that I unchecked the box to delete messages every 14 days while leaving the box checked "until I delete them".

That’s strange - I’ve used that for years and never had any issues with it, and you are free to check both. Besides, these settings should only affect message deletion, not logins for POP retrieval in any way.

Anyway, when I unchecked the "14 day" box on the account that had been functioning, it started having the same problem as the other one.

So it started having login issues and caused the exact same error message?

Also, I'm still getting the error about "sending of password did not succeed".

Did/can you remove the stored password in Options > Security > Passwords tab > Saved Passwords… ?

Also, I don't see an update tab.

The tab should reside in the Advanced settings as described here.

What are the versions on both systems? You should see them in the Check for Updates dialog as shown here.

So - so far it seems to be solved. I've been able to connect for the past 24 hours.

I manually removed the password for the account (in thunderbird). I changed the password on the webmail site. I removed the account (in thunderbird) and reinstalled it with the new password.

Thanks to everyone for the help.