gh-86650: Fix IndexError when parse emails with invalid Message-ID (GH-117934)

In particularly, one-off addresses generated by Microsoft Outlook:
https://learn.microsoft.com/en-us/office/client-developer/outlook/mapi/one-off-addresses

Co-authored-by: fsc-eriker <72394365+fsc-eriker@users.noreply.github.com>