Question about deleted emails (emails being marked as deleted)

[Denis BUCHER]

Hello,

Many email clients simply marks emails as deleted when moving them or 
deleting them ? Which makes a huge amount of "ghost" emails filling our 
server.

Is there a way with a simple script to delete all deleted emails let's 
say older than 30 days ?

Thanks a lot in advance for your help !

Denis

cyrus version :

name       : Cyrus IMAPD
version    : v2.2.12 2005/02/14 16:43:51
vendor     : Project Cyrus
support-url: http://asg.web.cmu.edu/cyrus
os         : Linux
os-version : 2.6.16.46-0.12-smp
environment: Built w/Cyrus SASL 2.1.21
              Running w/Cyrus SASL 2.1.21
              Built w/Sleepycat Software: Berkeley DB 4.3.29: (March 28, 
2007)
              Running w/Sleepycat Software: Berkeley DB 4.3.29: (June 
16, 2006)
              Built w/OpenSSL 0.9.8a 11 Oct 2005
              Running w/OpenSSL 0.9.8a 11 Oct 2005
              CMU Sieve 2.2
              DRAC
              TCP Wrappers
              mmap = shared
              lock = fcntl
              nonblock = fcntl
              auth = unix
              idle = idled