Fatal error: failed to mmap cache file

[Ian P. Christian]

I have a mailbox on my server wither just under 6600 emails in it.

The cyrus.cache file is 1/2 a gig in size:

# ls -lah cyrus.*
-rw------- 1 cyrus mail 536M Mar 27 13:46 cyrus.cache
-rw------- 1 cyrus mail  171 Mar 27 13:12 cyrus.header
-rw------- 1 cyrus mail 386K Mar 27 13:46 cyrus.index


When a user attempts to access their mailbox, I see this in the logs:

imaplo[29053]: login: localhost [127.0.0.1] postmaster at domain.com 
plaintext User logged in
imaplo[29053]: IOERROR: mapping cache file for 
domain.com!user.postmaster: Cannot allocate memory
imaplo[29053]: Fatal error: failed to mmap cache file
master[29953]: process 29053 exited, status 75
master[29953]: service imaplo pid 29053 in BUSY state: terminated abnormally


Can anyone suggest what might be causing this?

Kind Regards,

-- 
Ian P. Christian ~ http://pookey.co.uk