my zimbra and os
CentOS release 5.8 (Final)
Release 7.1.1_GA_3196.RHEL5_20110527011124 CentOS5 FOSS edition.

when a user from my domain sends an email to an other user from my domain the email goes into spam, and because i use diferent clients the spam folder isn,t accesible for them.
is there a way to put my domain into a safe sender list?