Hi @Raúl Aurelio Pinedo ,
- IMAP will not be removed in 2021. According to Microsoft’s official statement, OAuth 2.0 support for the IMAP protocol is already supported in Exchange Online.
For more information you could refer to: Announcing OAuth 2.0 support for IMAP and SMTP AUTH protocols in Exchange Online and Authenticate an IMAP, POP or SMTP connection using OAuth - According to the article provide by Microsoft, the end date for Basic Authentication on Exchange Online previously was Oct. 13, 2020, but Microsoft is now pushing it out due to uncertainties surrounding the "COVID-19 crisis." However, starting from October 2020, basic authentication for new users will be disabled by default, and basic authentication will be disabled for existing users who do not have basic authentication usage. If the users in your organization meet the above conditions, then your understanding is correct, and some users may be prohibited from using basic authentication.
When you disable Basic authentication for users in Exchange Online, their email clients and apps must support modern authentication. Those clients are:
Outlook 2013 or later .
Outlook 2016 for Mac or later
Outlook for iOS and Android
Mail for iOS 11.3.1 or later
For more information you could refer to : Disable Basic authentication in Exchange Online - In addition, Microsoft has stated that it will prohibit the use of basic authentication in the second half of 2021. Blocking Basic authentication can help protect your Exchange Online organization from brute force or password spray attacks. If possible, it is recommended that you enable modern authentication as soon as possible to replace basic authentication
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