Malformed Message-ID causes bad Archived-At header

[rpcross]

Some messages in the archive have malformed Message-ID headers that look like this:

Message-ID: <2022121415465349496212@chinaunicom.cn>+262AC600C9AAF174

Which cause incorrect Archived-At header computation. The implementation in Mail Archive, using Python3 email.EmailMessage handles this field properly. When Postconfirm is migrated to Python3 ensure that this scenario is handled properly.

Example:
https://mailarchive.ietf.org/arch/msg/auth48archive/hcvPTMHdX352X228HPoFgqGbd78/