Add support for sending emails through Microsoft Graph

[rjgoyln]

Summary

Sending mail from an Office 365 or Outlook cloud mailbox is expected to go through Microsoft Graph, and with EWS gone the SMTP relay into those mailboxes is the last legacy path standing. Airflow could only reach them over SMTP, so a deployment on a Microsoft tenant had no supported way to alert on task failures from its own mailbox.

Change

The Azure provider sends mail through the Graph sendMail endpoint over an existing msgraph connection, covering both places email is configured: [email] email_backend for email_on_failure and email_on_retry, and MSGraphNotifier for the state-change callbacks. The notifier implements async_notify, so it also runs in the triggerer.

from_email selects the mailbox to send from, and Graph addresses that mailbox in the request path — hence the parseaddr, since the option is conventionally configured as Display name <user@example.com>, the form SMTP and SES accept. Attachments ride inline in the request body rather than through an upload session, which is what bounds them at 3 MB.

The email backend contract is synchronous while the Graph hook is async-only. The sync entry point therefore runs the coroutine on its own loop and closes the request adapter before that loop goes away; the cached adapter would otherwise outlive asyncio.run bound to a closed loop and break the next email.

closes: #71541

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Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Opus 5)

Generated-by: Claude Code (Opus 5) following the guidelines

[dabla]

I will try to review this PR tomorrow as I may have some remarks, but I like this, very nice and needed addition!

[dabla]

Congratulations @rjgoyln, nice work on this PR as this was a most needed feature especially with notifications.

[rjgoyln]

Thanks for the review. Really appreciate it!