https://support.mozilla.org/en-US/kb/problems-sending-and-receiving-messages

I looked over those pages and all the settings seem right. I actually have two computers using the same internet. Both use Thunderbird with microsoft email. One computer has thunderbird using a live.com ending email address and that is working fine. The other one has thunderbird using a msn.com ending email address and that is the one that is suddenly failing all the time. Nothing appears to have changed. The settings in Thunderbird on both computers are the same except for the different username/email and password.

Have you tried logging into the MSN account using your browser. Hotmail (in it's many guises) are a little ham fisted, and if they have a message they want you to read or a change to their terms you musy acknowledge they will block mail client until you log in with a browser to fulfill their desire for you to click yes to something.

Yes I tried logging in via the browser and it works fine. There were no messages or anything like that. I actually logged in and changed the password and then put the new password in Thunderbird to see if it would help but it didn't.

had someone the other day here who had a similar problem, and the issue was some sort of password vault on their anti virus / internet suite. The program had the old password and was inserting it into the data stream so Thunderbird never displayed a password prompt, which it should be not as your stored password is not longer correct

I use the simple MSE antivirus and I don't believe it has any password storage vault or anything like that. Thunderbird does show the prompt fine and it appears to save the password correctly and the password does show up in the tools/passwords area/show password.

have you turned your computer off for a few minutes and turned it back on? and the Modem/Router?

Yes, I turned everything off for 5 minutes, computer, modem and router.

I tried a suggestion of someone else and created a new hotmail account as a test. I tried to pop it with TB and it failed to authenticate. I then tried to imap it and it worked. So something is screwy with the pop I guess?

Just tried to pop the hotmail test email on my good thunderbird on the other computer that is working fine and it failed to authenticate..

POP needs to be enabled on the live servers, IMAP does not.

Do you think it could be a microsoft side issue?

Following another suggestion, I pinged pop3.live.com from my computers CMD window and this resulted in timeouts and all packets lost.

so you have a firewall or DNS issue.

My guess would be firewall, but to be sure.

open a command prompt as administrator and execute:

 ipconfig /flushdns

That will flush your DNS cache and force a refresh. Refresh might take a couple of minutes and while it happens nothing much web based will work.

Hi. I actually had tried that early on and it didn't help. I tried it again now and I'm still getting the timeouts on pop3.live.com.

I use windows firewall on both computers. I took a look at it and nothing seems out of the ordinary (though I'm no expert) and no settings were changed as far as I know. Should I perhaps restore defaults?

Could it be something with the router that turning it off does not fix?

Edit: I tried changing my ISP DNS (get automatically) in the router to google dns and that didn't help. When I changed it back to the isp dns, it now no longer times out when i ping pop3.live.com.

However, the password still fails to authenticate. Tried deleting password on TB, restarting, entered it again, same problem.

I think I am going to try resetting the router.

OK, the pop3.live.com has gone back to timing out when I ping it.

I'm thinking that maybe when I changed to google dns this "fixed it" there was just a delay. I'm going to change back to google dns and see if it starts working again.

Ok, I tried totally resetting the router creating new passphrase and all that and that didn't work.

I'm gonna switch to google dns and check that out.

Update: Changing to google dns does not seem to be helping nor does changing it back to isp auto dns.

So I restarted everything and now it can ping but the issue with thunderbird remains. The password fails to authenticate.

One thing I've noticed now is when I restart everything, immediately after I can ping pop3.live.com. A short while later, the ping will time out again consistently.

In any case, thunderbird fails to login to the msn account regardless if I can ping pop3.live.com or if is timing out.

Here is an update:

I am able to ping pop3.live.com but the problem still continues exactly as before.

Something interesting I found is when I log into the msn.com email account via the browser, I discovered in the settings area there is a link to "recent activity". It shows every log-in attempt and if the attempt was made by my firefox browser or through pop3 and whether it succeeded or failed.

I actually tested it by trying to log in with thunderbird to make sure this is what is meant by "pop3". And sure enough the attempt immediately showed up under recent activity. All the thunderbird attempts to login are listed as successful logins with entrance into the account. Of course, on thunderbirds side, it fails to authenticate.

Edit: I tried to add a gmail account to my thunderbird as a pop and it worked fine. As mentioned before, If I try to add a microsoft email, it fails to authenticate.

Edit 2: I still sometimes can't ping pop3.live.com. It's back and forth.

Ok I solved the problem.

I looked through all the settings in the hotmail/msn account and found something called 2 step verification was active on the account. I don't recall activating it but I deactivated it and everything works fine now.

Here's some info about 2 step verification and mail apps:

http://windows.microsoft.com/en-ca/windows/two-step-verification-faq

Quite helpful. If you want to keep two-step verification (which is more secure, after all), then you need only generate an app-specific password for Thunderbird (and other 'dumb' apps). Each account protected by two-step verification has a function to generate these unique passwords.