[Exim] Frozen incoming messages?

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
For some reason, exim is freezing some of my incoming messages then
delivering them to me hours later.... This is really confusing because
my e-mail program says I have new e-mail, but it's buried below many
hundreds of incoming messages and very hard to find. Any suggestions?
--