Now more than ever, you should disable your legacy authentication in Exchange Online, last year Microsoft announced that they will remove that basic Authentication next October (https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-may-2022/ba-p/3301866)

Did you know that:
- More than 99 percent of password spray attacks use legacy authentication protocols
- More than 97 percent of credential stuffing attacks use legacy authentication
- Azure AD accounts in organizations that have disabled legacy authentication experience 67 percent fewer compromises than those where legacy authentication is enabled
Disabling legacy authentication for users is a must-do on your identity security checklist
Why? becasue is a security gap and Microsoft took a lot of effor to promote Modern Authentication. So, you can disable now this basic Authentication in very simple steps:

If you don’t want to use this option, you can block the access to those protocols by using Conditional Access, understanding in a very simple way the impact of the policy.
What are you waiting for?