SMTP authentication on Exchange 5.5 or Mail Marshal

To require SMTP authentication on an Exchange 5.5 server:

To require authentication for inbound connections:

1. Click the Connections page.
2. In the "Accept Connections" Section, mark the radio button for "Only from
hosts using Authentication."

But beware, if you have a server that is accessible from the internet, most mail will be bounced back. Because most of the SMTP servers on the Internet
only support Anonymous Authentication, inbound sessions from external SMTP servers will be affected. Only use this if you control the other end of the SMTP connection.

Sorry - I should of been more clear - I need to authorize the outgoing connection to our mail relaying server at the isp

I did find another way around the problem just before I saw your response but this does look like it was what I needed so here are the points and thank you.