Route Subdomains to Sharepoint

I'm trying to get routing working for my subdomain.  Everything works internally but when users send from outside they get a bounce back.  I'm trying to route public email addresses to my SharePoint site. 

I'm getting "#550 5.7.1 RESOLVER.RST.AuthRequired; authentication required ##rfc822;".

In sharepoint all my items get created with a subdomain.  Ex:  contact@sharepoint.domain.com.  In order to route some email I added a @domain.com address as well, but the primary is sharepoint.domain.com.

So I thought that if contact@domain.com were emailed it would find it and route tocontact@sharepoint.domain.com.

David Jenkins