i've been using zimbra for past 5 months.. everything went well..
last week i change my isp connection so i got different IP for my domain and subdomain
right now i can sent email to internal domain, can receive email from internal and external , but i can't send email to external..
here's i got from zimbra.log
to=<firstname.lastname@example.org>, relay=none, delay=0.03, delays=0.01/0.01/0/0.01, dsn=4.4.3, status=deferred (delivery temporarily suspended: Host or domain name not found. Name service error for name=yahoo.com type=MX: Host not found, try again)
my mail server behind the DMZ , before this problem happen i didn't use split dns and everything went well..