Basic Authentication and Exchange Online – September 2021 Update

Thanks Greg Taylor - EXCHANGE , really appreciate your time to clarify things here.

I hope you understand I cannot base the response plan to this whole change for our product on hope. I am not sure whether I still miss something, can you please confirm or clarify and comment my understanding below?

MS will shutdown basic authentication for Exchange online from 1st of October. Basically any vendor or provider of software and systems which poll a central mailbox like service@ or sales@ to create cases from emails is affected. This is helpdesk, ticketing, CRM, workflow, case management and many more domains. Mail polling can simply stop working overnight from 1st of October unless

1) the sw vendor has implemented polling emails via Graph API and switched to modern auth there meanwhile and accepted the double work of maintaining two protocols for email polling

2) the vendor has implemented the mentioned Client Credentials Flow for IMAP feature which is targeted GA end of June. That leaves 3 months for dev/QA, rollout and upgrades of the whole customer base of our product. That's not a doable timeframe for us and not for any product vendor I assume.

Our only viable option seems to be to implement Graph API email polling now, but I still feel like I miss some back door or option out. We're a tiny fish but have all the Zendesks, Freshdesks, Salesforces etc. in the field realized all this and adapted their implementations to Graph already? Or is this mostly unknown and there will be a huge rage storm once October comes closer from that direction causing another lifesaver grace period for basic auth (making us the stupids who invested in a proprietary protocol implementation to maintain)?

I would appreciate your thoughts on the above or recommendations for software vendors relying on polling email in an impersonated way like us.