I (and I'm sure that I'm not the only one

a) Print the mail to PDF, pack it together with the attached data to a ZIP and name and save it. That's a lot of manual work, but fits to the ZIP-philosophy and needs not complex software for later usage.
That's what I do.
b) Save the file a a MSG. That's quick, but unhandy for later usage (file-format, searching, ..) and I never saw intensive usage of MSG-archives.
c) Print the mail to PDF and attach the attachment to PDF. That's a sophisticated way, but unusual - I newer saw someone who used attachements in PDF. How many percent of users know this function?
d) ... ???
So writing and thinking about it I think the way a) would be the best for a new feature. It could be not too complicated to implement - print the file, zip it with attachments, take the "subject" of the mail as filename for the ZIP.
What to you think about it?