Update 1/20/2022: We have edited this post for clarity based on customer feedback.
Over the last few years, we have invested heavily in Microsoft Graph to enable developers to access the rich data ...
Updated Jan 20, 2022
Version 5.0
Blog Post
Probir_Chatterjee
You can't and shouldn't use Basic Auth anymore (https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-and-exchange-online-february-2021-update/ba-p/2111904) as its unsecure and depreciated.
We are in the same situation as you trying to find a suitable solution that our customers would accept. Until we have the full functionality in the GRAPH API there's not much we can do except encourage our customers to provide "feedback" to MSFT and hope that the September 2022 date is postponed if enough customers and partners act. In our case we do a lot of very large volume email migrations (sometimes PB's of email data) either from onprem to O365 or from one O365 tenant to another. EWS gives us everything we need, to be able to push up to 35 TB per day into Exchange Online.
Let's hope once the complete set of functionalities is ported to graph that we will be able to do the same or more 🙂