Mails were flowing from MS Exchange hub 2010 to Ironport C160 through an old PIX515E,
After we change the PIX to a new ASA5500 the mails stopped flowing with following error
"The message has been queued on server 'jed-caht2.maaden.com' since 5/28/2012 9:27:37 AM (UTC+03:00) Kuwait, Riyadh. The last attempt to send the message was at 5/28/2012 9:36:54 AM (UTC+03:00) Kuwait, Riyadh and generated the error '451 4.4.0 Primary target IP address responded with: "451 5.7.3 Cannot achieve Exchange Server authentication." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.'."
please help to solve this issue