[plug] Sendmail relay authentication

[Paul Baumgarten]

G'day... everyone on holidays?  the list has been fairly quiet.

I have a bit of a sendmail relaying question for everyone

I want to be able to allow staff who connect to the 'net via their ISP of
choice from home to send mail using our sever.  I am using Sendmail
8.9.3-10.  With the current config anyone who attempts to do so gets the
"550 We do not relay" message.  Relaying is currently configured for our
internal LAN's IP addresses only.  Unfortuantely because it is impossible to
know what IP our staff will use to connect on, I can't establish a static
list of external allowed IPs.

I have noticed that most SMTP clients (such as Outlook Express, Netscape
Messenger etc) have a config option reading "My Outgoing Server Requires
Authentication" and you then put in the username and password.

Qu1.  Is there a way to enable Sendmail to turn on that "require
authentication" option for the relaying of mail?  Is so, how?  Currently the
only way my sendmail accepts/rejects the relaying of messages is based
solely on the originating IP address.

Qu2.  If not... one other possiblity I have considered is telling the staff
member they must check their mail first (requiring them to validate with the
POP3 server).  Is there some daemon software around that will watch the
secure log and upon a POP authentication, put the IP address of that the
authentication originated from into the /etc/mail/ip_allow file and then
killall -HUP sendmail ??

Qu3.  If the POP option is a no goer... what about some type of web-form
with a user name and password prompt.  The validate script then adds the
originating IP into said file and does the HUP thing.

The catch with idea 2 or 3 is that the newly allowed IP address for relaying
would then need to be automatically removed, say after a couple of hours.

Any other possible solutions to this that I am missing?

TIA

Paul Baumgarten (email: paul at kcc.wa.edu.au)
Information Systems Manager
Kingsway Christian College
157 Kingsway, Landsdale, WA, 6065
Ph: +61 8 9409 7078
Fx: +61 8 9409 6179