Handle exceptions thrown while getting message ID

[floriansnow]

Python's email library can throw both an IndexError as well as a HeaderParseError when the email has certain invalid data in the message ID. This prevents users with faulty emails from syncing. This change allows us to simply continue without a message ID as was intended in the code before anyway.

This v1.1 template stands in .github/.

This PR

Add character x [x].

• [x] I've read the DCO.
• [x] I've read the Coding Guidelines
• [x] The relevant informations about the changes stands in the commit message, not here in the message of the pull request.
• [x] Code changes follow the style of the files they change.
• [x] Code is tested (I ran this with a local copy of the code without issues).

References

• Issue #no_space

Additional information

Closes #119. I am wondering whether we should catch some more exceptions in similar cases and also fix things like #160 along the way.