Why oh why do folk think removing something will fix it. Either that or reinstalling.

Now we don't know what the original problem was, and have a new one sitting on top of it.

outlook refuses connections that occur in a time frame of less than 15 minutes. This is often the reason for the pop-up folk set the checking interval to less than 15 minutes.

So what anti virus do you use? If Nortons disable email scanning and sonar before you attempt to add a new account. Even better simply boot windows into safe mode with networking to get that problem product disabled properly.

Have you allowed access to IMAP on the outlook server? go here https://outlook.live.com/mail/options/mail/accounts click sync mail. If you are using POP enable it. Make the other appropriate decisions. Take note of the POP/IMAP and SMTP settings. Make sure the Thunderbird account wizard gets them right.

If you use two factor authentication with hotmail, have you created an app password for Thunderbird to use? Thunderbird can not use the thing that is sent to your phone.

I use Thunderbird,was not receiving any mail under two accounts.They were imap so I deleted both accounts and now cannot add them back,I need the messages that were in the inbox accounts.Get message account already exists??

Add to above message..kept getting messages "outgoing server not known",many error messages"Append Fioclose fail 54/31etc. "network error TWC disconnects error code 15339424,typing message ends up in draft folder..my internet provider says it is TB error.Now I need to get the 2 accounts I deleted back.I have tried everything I know to reset the accounts to no avail.

"outgoing server not known" the intermittent receipt of this message probably indicates issues with DNS. (that is system setup/ Network connectivity)

What anti virus do you use? For instance you have to uninstall Nortons with an uninstaller downloaded from their web site to actually stop it from it's interference. It can mess up the registry so badly that that is the only approach that works. WHile it is a "worst offender" it is not alone in it's ability to mess up windows and the internet for anything but their core "browsing" functions.

I suggest you try adding the account in Windows safe mode. 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.