You are probably using the POP3 server name
(eg: mail.mydomain.com) for the Mailer.RemoteHost property instead of
the outbound SMTP gateway.
The correct setting for the RemoteHost property is:
Mailer.RemoteHost = smtp.mydomain.com
where "mydomain.com" is your domain name.
Note: The prefix for the outbound mail services is set to "smtp." instead of "mail."
The "mail.mydomain.com" service refers to your POP3 server machine,
while "smtp.mydomain.com" refers to the outgoing SMTP gateway for your
domain. These are actually two separate servers.
The POP3 server cannot relay, only the SMTP server can. The reason you
could receive mail to your domain only is that it is physically located
on the POP3 server. When ASPMail sent the message, it delivered it to
the POP3 server. The POP3 would accept the messages to "mydomain.com",
since that domain is on the server, but it refuses to relay to domains
not on itself.
By telling ASPMail to use the SMTP service instead, it will deliver the
mail to the outbound gateway, which will then pass it on to its