This is using a single MS Exchange 2007 server. Recently, found that outgoing mails to a few domains always ended up in queue, and these mails eventually purged upon 2 days. On mxtoolbox, do not found that that the exchange Ip was blacklisted, and SMTP test passed. How should I troubleshoot and get this problem resolved? THe server os is w2k3 r2.
Thanks in advance.