I have running exchange server....every thing was going fine, however last two days I cannot receive any external emails from outside the network, while I can send/receive internally and send to external address too....
when I tried to send email from gmail I got the following error:
Delivery to the following recipient has been delayed:
***@***
Message will be retried for 1 more day(s)
Technical details of temporary failure: DNS Error: Address resolution of *****.dyndns.org. failed: Domain name not found
And the message never received...
Telnet output:
220 MAIL.****.** Microsoft ESMTP MAIL Service ready at Sun, 8 Mar 2015 09:31:16 +0400