Thanks, and I've tried setting my options in webmail prior to sending, but I am still getting errors when I send to some, but not all domains:
Final-Recipient: rfc822; email@example.com
Remote-MTA: dns; oncall-pc.com
Diagnostic-Code: smtp; 550-Verification failed for
<firstname.lastname@example.org> 550-The mail server could not deliver mail
. The account or domain may not exist,
they may be blacklisted, or missing the proper dns entries. 550 Sender
How do I allow a distant mail server to verify sender's validity? I get the feeling that this is some anti-spam measure that I'm up against...