I know this is an older post at this time, but aren't these two separate settings? If you are hiding the sender IP address and only allowing authenticated users to send email, they should each work independently and allow authenticated users to send emails without passing on their IP address. Perhap...

Hi all, I'm receiving two errors trying to setup Smart Host and I can't figure out what I'm doing wrong. 1) I keep receiving a relay authentication error. I have 2 servers, one is working fine as an email/iis server and I'm trying to setup a second one to point to it. I have setup relay security to ...