On April 8th, 2014, Thunderbird stopped working with Gmail on POP email. The problem was that the correct username and password could not be authenticated by Gmail (in particular if you are a heavy Thunderbird user and use the recent:username@gmail.com then you would get an error message saying that the username and password were not correct.)

It turns out that Google changed the method for going through different kinds of secure authentication. Roughly speaking, there are several different authentication methods the client can try. If the initial method is not acceptable to Gmail, then Gmail is supposed to allow other methods. However, instead of allowing other authentication methods, Gmail would stop immediately with an authentication error.

Here is a post from on a workaround for Thunderbird which works on version 2.x as long as you do not click the remember in password manager.

The short version is that in

Tools | Options | Advanced | Advanced Configuration | Config Editor

set

mail.server.default.authMethod to 2 (integer)

Guys, I posted this issue in the Bugzilla forums (https://bugzilla.mozilla.org/show_bug.cgi?id=993110), and chris_marino came up with one workaround:

It seems the problem is that Thunderbird sends AUTH PLAIN (a base64 encoded user+password) even if the server does not support it. If this fails, it them tries to use AUTH LOGIN but Gmail refuses to respond after the first AUTH PLAIN error.

There is a workaround. You can set this in the config editor:

mail.server.default.authMethod to 2

or

mail.server.serverX.authMethod to 2

serverX where X is a number coresponding to the account created internaly.

Also you can change it in the prefs.js file directly.

This means that AUTH PLAIN is not sent anymore and AUTH LOGIN is used directly.

This setting is not normally available in account settings, but it will show up as "Password, original method (insecure)" if it is changed in the config editor. If anything else is selected, you cannot select it back, you have to use the config editor again. Btw, there is nothing secure about AUTH PLAIN because it's an unencrypted base64 that can be decoded by anybody. Also, Gmail forces SSL encryption on all connections, so using AUTH LOGIN is ok.

It worked for me!!!