http://www.angio.net/misc/mail.html says the following:
Why use IMAP locally? If you refile messages between mail
folders directly using Mutt, you'll store invalid X-UID headers
into the wrong mail folders. When you then check your mail with
IMAP, the IMAP server will decide that you've goofed up your
mailbox, and renumber it for you, and change the IMAP
uidvalidity identifier. Isync will then barf. You could
accomplish this by having Mutt strip out the X-UID header on a
refile, but this way is much more clean.
Is this still accurate, or did it only apply to some 1.3 version and has
been fixed in 1.4?
--Greg