As part of Sharepoint 2010 installation for large manufacturing company in US we had configured several approval workflows. While we were testing the workflows we found that while the workflows got initiated it didn’t send out mails to approvers and showed the below error

 

“The e-mail message cannot be sent. Make sure the outgoing e-mail settings for the server are configured correctly.”

 

As the message indicated we double checked the email settings of the Sharepoint server and it had  valid exchange server address. Then we are looking at ways of verifying connectivity between the exchange sever and the Sharepoint server, good old Telnet came to our help. Using telnet command we found out the issue was because specific email domains were restricted.

 

More information on checking connectivity using Telnet can be seen from this Microsoft Kb Article

Telnet is not installed by default in Windows Server 2008. To find steps for installing telnet client look here