Are you using 2 step authentication on your outlook accounts? If so you need to create an application password at outlook to use with Thunderbird. This article discusses the process. https://www.lifewire.com/access-outlook-in-thunderbird-3572532

I went very carefully through the entire ordeal of setting up a two step verification and still have the same issue.  :(

I was not suggesting that you had to activate 2 step but that you had to use the app password if you are.

I have seen it reported that some antivirus software gets in the way of adding accounts to Thunderbird. If you start your computer in Safe more with networking can you add the account?

It's been a while for my response here, and sorry about that. Severe thunderstorm hit, knocking out power for a day, and trees down so lots of yard work.

I misunderstood the 2 step auth., so my bad. I've cleared that up and it's turned off on the one acct. I set up with it. I tried all the accts. via safe mode and same issue. Thunderbird never connects, says it times out. I used an outlook.com email with thunderbird a couple years ago and it was super easy to set up. No issue whatsoever, so can't figure this out. It times out on every acct. I have and try. Any more suggestions anyone? Would really appreciate the advice.

Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

Safe mode did not fix the issue. This is a clean install of windows 7 with only windows updates, Frontier Secure (anti-virus from Frontier internet service provider), Firefox, Thunderbird, and CCleaner installed. I have tried setup and retrieving mail with the Frontier Secure completely disabled as well, but same issue.

Since I couldn't get Thunderbird to work last week after a fresh 7 install, I wiped the drives and started from scratch, making Thunderbird a priority install, ahead of anything else.

Have you modified ccleaners default settings to not interfere with Thunderbird? By default it deletes settings and passwords which confuses many.

Other possibilities include. A password with more than 8 characters. Hotmail had that limitation in the past. I have no idea if they every fixed it.

Have you confirmed your settings on outlook.com? My blog post has directions on locating them in the outlook web site. https://thunderbirdtweaks.blogspot.com/2016/06/hotmail-proxy-errors.html Then there is the manual approach of actually attempting to log into the server using telnet. very old style command line stuff. but it does give good feedback on failure. Instructions here https://mediatemple.net/community/products/dv/204404584/sending-or-viewing-emails-using-telnet Telnet is not installed by Windows by default, but is one of the accesories available for intall. I do not suggest you actually try and read your mail using it, just try and log in.

I tried "telnet outlook.office365.com 995". (without quotes of course) It showed connecting for around 5 minutes then, "could not open connection to the host, on port 995: Connect failed." Then tried "telnet stmp.office365.com 587" with same result. Those are the pop3 and stmp shown in the POP/ IMAP/ SMPT email settings configuration at outlook.com

I did a second test out of curiosity. On both desktop comp. I'm trying to get email on, and a laptop I have, (both win7 professional) I set them up with windows live mail, Thunderbird Mail, and MailBird Mail. I had never set up any email on the laptop before. All three mail clients on both computers failed with "timed out" and "address or password incorrect"... even though they work perfectly going into the outlook.com site and my email accounts.

The new install of win7 on desktop was meant to reorganize everything after nearly 8 years of scattered folders I couldn't find anymore.  :) . I took screenshots of every setup screen of nearly every program I had, every page of BIOS, windows live mail 2012 settings, Thunderbird settings I used a couple years ago or so, and many months ago took screenshots of every page of setups on each individual email account at the outlook.com website as well. That's how I know everything is identical on the desktop computer.

That made me remember I had an email problem before. I checked connect history at outlook.com, it shows my last successful sync of email accts. via POP3 on all, was 6/25/2018. That's the other reason I wanted to reinstall windows. I thot my messy hard drives were causing issues.

Thanks again for your help

oh, uninstalled CCleaner as well, so that wasn't the problem.

Clearly a firewall issue I think. so did you get any new hardware like a modem or router around the time of failure? Most modern routers and modem have an inbuilt firewall and I am seeing stuff from internet service providers becoming increasingly restricted in the ports they default enable.

All the internal hardware is a minimum of 8 yrs. old, no external devices of any type have been connected, and modem is from internet provider and has not been changed on settings in 4 years (when I received it). I have turned off all anti-virus, which is the same as I had before issue, and it updated last in January this year, and even went to the extent to shut down windows firewall as well, and uninstalled anti-virus. It's like every email client tries to send the password to outlook.com, and outlook is rejecting it.

Oh, and no anti-virus protection on laptop. It's only used for youtube and now this site. Don't have anything stored on it or use for any other purpose. Hey it's only ebay valued at $25.  :)

Well, you were right... it was a firewall issue. I never thought to check the modem/ router from the internet supplier, especially since nothing has been changed since it was hooked up 4 years ago. Interestingly it was set on medium security so I moved it to low. Still nothing. Moved it to firewall off position, and guess what!!! Email works. Hmmm... I'll contact the provider tomorrow because obviously I can't leave firewall completely off, and something has gone awry with the router.

Thanks so much for pointing me in the right direction, even if it was inadvertently.  :D Appreciate you taking the time to help me.

more experiments.

from a command prompt. (windows key + X type

tracert imap-mail.outlook.com

While I do not expert you to understand all the returned hops. the first few are internal to our home. then you will see tings names after you ISP and then msn.net.

How far does the trace go? does it even leave you local machine? Hop 1 is 7our local machine usually a number starting with 192. or 10. how far it gets might be interesting as it uses different ports to mail.

Just read your last post, sorry about the crossover.

in the firewall section open the ports outlook are telling you to use for your mail that is probably all that is needed. 993 and 587 if I recall correctly

Been a very long day after going to bed at 1am after your help last night.  :) Thanks again. You are correct, I need to open the ports, but my internet provider said they will not tell customers how to open ports, soooo...

I have a netgear D2200D-1FRNAS modem/router from IP. I've looked for opening port examples online but can't find any exactly like this modem to follow, and do I need to open ports in windows firewall as well? (Win7 Professional).

There is a manual here https://www.manualslib.com/manual/1273545/Netgear-D2200d-1frnas.html

Even though this is a n ISP only product not supported by netgear and probably of poor quality.

I am interested if this was the default your provider sent, as it might be of considerable interest to other Frontier users that have trouble with their email.

Thanks. I'll check more on it tomorrow and see what I can figure out, and will let you know tomorrow evening.