a350e2047d
It seems some tools try to interpret the filename of message files, even though they shouldn't: "Do not try to extract information from unique names." In particular, they seem to interpret the first part of the name (before the first dot) as the # of seconds since the Unix epoch (ie., time(NULL)). That's not what mu/mu4e put there. So, let's conform a bit more to the expected filename (as per the maildir spec), so we're not confusing those tools.