I am having the same problem with the e-mail servers that SBC uses. While it is a good suggestion to use the SME server for outgoing SMTP, it doesn't always work. A lot of ISPs and especially AOL are now denying any SMTP traffic from residential/dynamic IP numbers. So SME needs to use the ISP's e-mail as a helper - but it requires authentication.
An even greater evil is that SBC also requires the sender's reply address be the SBC e-mail account. So even if I could get it working, I cannot have the reply-to address meet the requirement. The company that hosts mydomain.com will allow me to upstream to their SMTP, but I need to authenticate with them.
Summary:
client -> SME SMTP -> user@aol.com : Fail, non-authorized SMTP.
client -> SME SMTP -> SBC SMTP -> user@aol.com : Fail, authentication required at SBC.
client@mydomain.com -> SBC SMTP -> user@aol.com : Fail, non-SBC account.
client@sbc.com -> SBC SMTP -> user@aol.com : Successfull, but not the desirable configuration.
client -> SME SMTP -> Hosting SMTP -> user@aol.com : Would work if I could authenticate.
In my case, the hosting company created a POP account that I need to check every 15 minutes or so. That will keep the public IP of my SME server (and it's users) in their authenticated list. I am going to mess with a test box of SME and see if I can get this all working.
Let the confusion begin...
Robert