How do I stop the Yahoo sign-in request pop-up on my Outlook 365 Inbox?

Thanks Kimberly. I'll give it a try!

Unfortunately, no information was provided for the questions asked pn July 30th. You may want to review my eariler responses.

Bottomline, the only way Outlook would ask about any Yahoo account is if an existing account is configured which uses Yahoo servers. Would have absolutely nothing to do with any stand-alone Yahoo account otherwise.

I fixed this problem by going to outlook's account information/account settings/server settings and found that yahoo.com had replaced my original server settings. I reconfiguered this with the original server settings and the yahoo popup went away. This change occurred without my knowledge so I'm unsure how it happened originally. You might want to perform a deep malware scan first to make sure that it does not happen again.

I fixed the problem in 2019 Outlook Office. Change the in and out email server settings on each email address from Yahoo.com to att.net.

I have the Office 365 on my PC and running 3 email accounts on Outlook (Hotmail, Live, AT&T). I understand AT&T is now Yahoo and config is a bit different than the others. Keep in mind, I am a novice.