To be honest I am not very familiar with SELinux at all.
If you run the following command as the Zimbra user, are all ports accessible?
nmap `zmhostname`
IIRC, I think there was a SElinux user that had devil of time (same issue I believe). I think there was a selinux config file that needed to be changed. Sorry I can't be of anymore help in the SELinux dept.
