On day the Send To option lost the Mail Recipient option from a clients Windows 7 system. The client was using Outlook 2010 and the typical solutions posted that suggested creating a new Mail Recipient didn't work.
The following solution did work for our client.
Diagnosing e-mail issues is often a time consuming task. Having your e-mail address, especially a corporate domain, blacklisted on a private list is even more troublesome. Each vendor has its own process and Comcast has their own as well.
Reporting Blocked Email
The SMTP Server Connection Diagnostics Tool is a free utility will enable you to troubleshoot SMTP Server issues more easily than using telnet. It supports both open and SSL connections and contains a built-in library of commands such as EHLO, DATA, RCPT TO, etc.. Nothing to install, just run the executable and step through your commands.
After completing several updates on Exchange 2013 due to another issue, we found that e-mail messages were going to the Drafts folder instead of the Sent Items folder. In addition the server was not receiving any messages either.
After further investigation we found that the Mail Transport service was failing, not immediately, which was why we didn't notice it after it was started. In this particular case the client had a secondary SMTP port configured for relay messages but that port was setup on both the Exchange 2013 CAS and Database servers but only one of the CAS server actually had the IP address assigned on the NIC. Once the relay SMTP port configuration was removed from the Database server the Mail Transport service ran fine and mail flowed through the system correctly.