Hi there!
Not all MIME boundaries contain timestamps. According to RFC 2046, a boundary delimiter line can be as simple as this:
---
with a closing boundary delimiter line of:
-----
Or something like:
--foo
and to close:
--foo--
The example you posted doesn’t ring any bells. Hopefully, someone else from the community can place it.
In some cases, even if the boundary delimiter was based on a timestamp, it may not be trivial to decode it. For instance, I have seen implementations where the software takes the current time and then hashes it before using it as the boundary.
The local part of that message ID lines up with a GUID. So, my guess is that it does not represent a timestamp. To confirm, I would recommend finding a number of those and observing how they change. If the digits change rapidly and randomly, it is unlikely that there is a timestamp there that you can decode. If you see some repeating patterns, there is hope 