Quoting Chris O'Regan chris@encs.concordia.ca:
Unfortunately, with IMP 4.x we are limited to the API provided by c-client/PHP imap module. This API is *horribly* inefficient and does all sorts of terrible IMAP things that are unnecessary/inefficient/embarassing. So it is conceivable that the entire mailbox is scanned when a mailbox refresh occurs.
I discussed this with our network administrator and he is not convinced since we weren't seeing this problem prior to the migration to Dovecot a couple of weeks ago (and the last time the user was seen logged in prior to last Thursday when he reappeared and the problem started).
It's just peculiar that we are seeing a problem with only one user. I have a feeling that the corrupt cache files are related since no other user has triggered these messages.
I would agree with the statement that this may be an issue due to a
certain user/mailbox - I was not suggesting that IMP requires a full
mailbox rebuild on every access for every user (yuck). But just in
case you started directly debugging the IMAP traffic, I just wanted to
throw out a warning that you will definitiely see some queries that
are extremely inefficient (e.g. c-client has a weird "lookahead"
configuration that will grab information for the 20 messages
immediately following the queried message, even though none of this
information is needed). To help in debugging, didn't want you/anyone
else to think this was an issue with either Dovecot or IMP.
michael