Office 365 Outlook Sign in issue

[Noman_Sarwar]

Dear team,

I have two users email ID having POP account along with Microsoft 365 business apps and Exchange online kiosk License which are not being sign in through outlook getting an error that your email server rejected your login. While the same user can access through web outlook with the same credentials. It was working fine previously and suddenly it started giving me error while other apps are working fine. I tried to configure the IDs on different system but getting the same error.

[#2]

Check if you have security defaults enabled, as this will disable basic auth and older protocols such as POP/IMAP wont work.

[#3]

@Vasil Michev  Where can I find this option, can you please guide me?

[#4]

Under the Azure AD portal: https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/concept-fundamentals-security-d...