Can't receive mails from specific email domains

[urielv]

Hi.

Recently we are having problems receiving external mails, but not from everyone, only some specific senders. Some of them are never received, others took days but finally arrive. The senders don't receive any error message, but their mail is never received.
The problem begun after we had a power failure and the servers shut down, as well as routers, switches and all the network equipment.
We work with Zimbra Collaboration Suite 7.1.0, on Red Hat Enterprise 5.0, virtualized in vmWare. I have added the domains in the salocal.cf.in whitelist, with no satisfactory results.
What troubles me is the fact that only some domains are rejected, without any error message or something that gives me a hint on what's happening,

[Yves Pires]

looks like a DNS problem

make sure your DNS server is working correctly first.