After working normally for a week or so, my Zimbra install has decided to stop doing proper MX lookups for outgoing mail, leaving me unable to send mail to any domain who's main IP (domain.com) is different then it's mailserver's IP (whatever host listed in MX record). My nameservers are working - 'dig MX domain.com' returns the correct information. An example is gmail. Postfix reports timeouts trying to connect because it is trying to connect to the IP referenced by gmail.com. This is M2 running on CentOS 4.