Since we announced in 2019 that we would be retiring Basic Authentication for legacy protocols we have been encouraging our customers to switch to Modern Authentication. Modern Authentication, based ...
Published Apr 19, 2021
Version 1.0
Blog Post
Greg Taylor - EXCHANGE
Microsoft
MicrosoftMarcusGoldsteen - if you want to export any email that is currently in your online mailbox to pst, using the good old way you've always done it - then you will need to re-enable POP in your tenant, get connected, and then do it. Basic Authentication Deprecation in Exchange Online – September 2022 Update - Microsoft Community Hub
Then do something else.
Again, doing this, because of 'overflowing data and crashing mailboxes' honestly, seems like a bad idea. As someone who has many years of email in his mailbox, and gets quite a lot of email - without issue... I'll say your issue isn't common. Update your process, copying emails to USB keys in different locations isn't a solution anyone should really be doing in the 21st century.