Added a second domain using the following steps:
1) setup a second accepted domain in hub transport as an authoritative domain
2) added my new email address to my mailbox settings (email@example.com)
3) set up the new email address as an IMAP account in Outlook 2010
I was able to receive email from outside and inside my organization and send email internally. I just couldn't send externally and got the NDR message '550 5.7.1 Unable to relay'. I did alot of research and found that my issue may lie in my default receive connector security settings. The changes were to uncheck the security mechanisms on the "Authentication" tab and check the "Externally Secured" option. Then on the "Permission Groups" tab I unchecked the "Anonymous" option.
Keeping in mind that these changes were made to the Default Receive Connector, have I opened up a security risk by selecting the "Externally Secured" option?
I unchecked the "Anonymous" permission group in an effort to close any gap. I don't want this to be an open relay server. I just need the single exchange server to send\receive for both domains.
Here's what I have....
domain 1= abc.com (original)
domain 2= def.com (additional)
firstname.lastname@example.org email is setup as exchange email in Outlook 2010. email@example.com is setup using IMAP for same person in Outlook 2010.
Screen shots are attached