Support for MS Graph

[nicokant]

I noticed that there is a package already published on pypi named django-msgraphbackend, but it doesn't seem maintained.
The core implementation is a few lines of code, so it should be an easy fit in anymail :)

[medmunds]

[As always, people can express support for this request by upvoting the initial post in the discussion.]

I'm having trouble telling whether or not the MS Graph Email API is a good fit for django-anymail. The API seems designed for managing a user's or organization's Exchange data. It's in many ways like a scriptable version of an Outlook email client, from what I can see, which is very different from most ESP's APIs.

Here are some typical criteria for adding an ESP to Anymail:

• ✅ Has a transactional sending API: https://learn.microsoft.com/en-us/graph/api/user-sendmail.
• ❌ Has "extended sending" options that Anymail could normalize (metadata, template merge data, delayed sending, etc.): I don't think so? (Though maybe tags & metadata could be stored using an extension?)
• ❓ Has webhooks for delivery status tracking events: you can get webhook notifications for a message folder, but I can't tell if that would report the kinds of sent/delivered/rejected/bounced/spam events that Anymail tries to normalize.
• ❓ Has webhooks for inbound email: that same "watch a folder" webhook maybe would allow this?
• ❓Anymail could set up a free or low cost integration test account. It seems like Microsoft does offer some sort of developer access to a test Exchange server with the graph API, but it's unclear if we'd need an enterprise account or a paid Visual Studio Pro subscription first. (And it sounds like maybe inbound email is not permitted on the test server in any case?)

The most important ❓ is the last one: having access to the API for development and ongoing testing. (I'm unlikely to look into MS Graph any further until someone can figure that out.)

Btw, it looks to me like django-msgraphbackend is being maintained. (I see the repo owner actively participating in PR discussions a few weeks ago. And while its last release was a little over a year ago, I don't think there have been any django.core.mail changes that would have required a new release since then.)