Exim + POP3 + quota problems

[Marcin Owsiany <porridge@skynet.com.pl>]

Hi!

Here's my setup:

 - a potato box (sounds cool, doesn't it? :-)
 - exim delivers mail to /var/mail/<user>
 - qpopper is my POP3 server
 - there is a user quota for /var partition
 - /var/spool/pop is a symlink to /usr/local/pop
 - there is no user quota for /usr/local partition
 - all users use POP3 to fetch their mail
 - also, a few users do read mail via local MUAs,
   so disabling locking in qpopper is not possible

The problem is that from time to time the following thing
happens:
 - the size of a user's mailbox in blocks becomes equal to the user's
   quota on /var
 - because the user may not use any more blocks on that partition,
   qpopper is unable to create a lockfile (/var/mail/<user>.lock)
   and exits with
   -ERR maillock: cannot lock '/var/mail/foo': 1
 - because of that the user is unable to fetch her mail

How do you guys cope with that problem? The only solution I could come
up with is switching to Maildir delivery, but might be painful...
Maybe there's some solution I've overlooked?

Marcin
-- 
Marcin Owsiany <porridge@skynet.com.pl>          http://marcin.owsiany.pl/
GnuPG: 1024D/60F41216  FE67 DA2D 0ACA FC5E 3F75  D6F6 3A0D 8AA0 60F4 1216