All, thanks for all the input in regards to this subject, however there are some small gaps that I've found myself in need of help.

I have a single zcs 5.0.4 GA (see signature) that hosts 3 external domains (,, and host my own internal domain (mydomain.dba) I have 2 internal DNS servers with A/MX records pointing to host mail2.mydomain.dba with ip, the external DNS servers point to the firewall which forwards port 25 traffic to

It all works well, I've done the split DNS test and realized that my internal DNS servers did the job right. All my users can send and receive mail for the most part. All my internal Scanner/Fax machines can send e-mail to the internal users and relay to most of the external. So I assumed it is all OK until AOL, Comcast, RoadRunner and some others decided to filter spammers by requiring reverse DNS lookups. I guess I do so too, but here is my problem:

I have an internal server with an internal hostname that will NEVER resolve to anything, except on my internal network. I get SMTP responses from AOL that mail2.mydomain.dba does not resolve to via reverse DNS. I've attempted to change zimbra_host_name to be the same as the external MX record of that will resolve to but for some reason it did not work when I tested it (did not restart services at the time). I have also changed the /etc/hosts file to resolve " mx" as the second entry below the localhost entry. Some how I cant get host `hostname` to display anything but the command prompt as either su - zimbra or root. My host name is still mail2.mydomain.dba. When I type zmlocalconfig it shows:

zimbra@mx:~> zmlocalconfig | grep host
ldap_host = mail2.mydomain.dba
logger_mysql_bind_address = localhost
mysql_bind_address = localhost
snmp_trap_host = mail2.mydomain.dba
zimbra_server_hostname = mail2.mydomain.dba
zimbra_zmprov_default_soap_server = localhost

So here are my questions: 1) how can I change the name that the HELO/ELHO uses for host name to reflect my external mx record. 2) By doing so, what other changes I need to make to zimbra, LDAP, MTA, etc. so that my users can send to those domains that REQUIRE public hostnames that resolve to Public IPs.?

Can you think of other hostname related entries that may be affected if I change the actual hostname of the server?