Cannot send email using OutlookExpres

[apcmlee]

Dear all,

Under Redhat 8.0, the mail server has been built using the sendmail, The clients can send or receive email in the intranet (with IP:192.168.0.x) Using the computers outside the intranet, the client can receive email but cannot send using Outook Express. With the error message as follow

RELAYING DENIED, connection port:25, SSL:none, server error:550, error code: 0x800CCC79

Why? I will appreciate much if there are any helping hand, thanks a lot

Regards,
Simon

[jstarkey]

Disclaimer: I'm a Qmail user. I haven't done anything with sendmail in years. But:

In order to prevent spammers from using your server to send out spam, you need to explicitly tell the server who may relay mail through it. Otherwise, you'd be running an open relay which is a very bad thing.

This should get you started, as well as explain the principles.

http://www.sendmail.org/antispam.html

[dalecosp]

Generally, in /etc/mail/relay-hosts:

192.168.0

or something like it should do the trick. quid pro quo: I'm into BSD, your actual file location may vary....