Microsoft turned off the basic authentication for IMAP and POP. IMAP allows users to access email stored on mail servers (e.g., Office 365). The Internet Message Access Protocol (IMAP) functions best when emails are accessed from multiple computers. Modern Authentication supports Multi-Factor Authentication.Modern Authentication is a more secure method that is based on OAuth 2.0 for authentication and authorization.Modern Authentication is the replacement for Basic Authentication.This change does not affect SMTP AUTH, as Microsoft will continue to support Basic Authentication for it in Exchange Online.Microsoft will stop supporting and retire Basic Authentication for Exchange Active Sync (EAS), Post Office Protocol (POP), Internet Message Access Protocol (IMAP), and Remote PowerShell (RPS).Basic Authentication is an outdated authentication method in which the email client passes the username and password with every request.Update on Basic Authentication retirement by Microsoft If wish to add another account via device,Click File Menu -> Choose Info -> Add account.Outlook inbox is opened in our device and test email message is received in Inbox.Open Run and Type Outlook profile name and click OK.To Open Outlook 2016 profile using our device,.If want to create another window, Choose Add another window.After Completed Successful testing, close the status page window.After clicking OK button, it return to IMAP settings page.Set Server Timeout as 10 seconds.If choosing short type it test shortly and display the result.If choose Long it takes more time to complete.Click Advanced tab to assign server port number and encrypted connection.Select the option, My Outgoing server(SMTP) requires authentication for configured settings for incoming mail server.In Mail settings, Verify your created Mail Account.Click next tab for outgoing verification.Click More settings to check Internet Mail Settings address.Specify Office 365 mail server address for Incoming and outgoing.Mention Office 365 Email id in user information.Enter mail server settings for IMAP account.

Choose POP or IMAP option to create Email account.Here, Office 365 configuration using IMAP.Outlook contain three types of manual setup creation

Add mail account to outlook 365