I want to let POP3 users who authenticate by sending credentials to the mail
server send email messages from outside the office, but I want to prevent
all other relaying. On my organization's SMTP virtual server, in the
Properties dialog box, I select the Only the list below and the Allow all
computers which successfully authenticate to relay, regardless of the list
above check boxes. However, these selections don't accomplish what I want.
When I send an email message from an Outlook Express machine outside the
office, I get a 550 5.7.1 unable to relay for <addressee> error. However, if
I select the All except the list below check box, everything works smoothly.
Why doesn't my initial set of selections work?