Hi @Jane Sinski
Welcome to our forum!
For better research, please provide more details about this case:
What is your account type? (Microsoft\Gmail\Other)
Is the problem happening on the client side or on the web side?
Will this be the case with all emails?
Can you provide a screenshot of the password requested? (Please be careful to hide your privacy)
There are many reasons that lead to this problem, try the solutions provided in this article: I can't send or receive messages in Outlook - Microsoft Support.
Also, if you're using an outlook.com account and you're experiencing a password pop-up issue, you may have encountered a recent temporary error. More information, see: Outlook and other apps are unable to connect to Outlook.com - Microsoft Support.
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