+++ Raju Mathur [linux-india] <02/12/01 20:41 +0530>:
> Couple of questions about sendmail.  I enabled SMTP AUTH (using the
> Cyrus SASL and PLAIN and LOGIN methods) on a stock Red Hat 7.1
> Sendmail 8.11.  The LOGIN works fine for local users relaying mail
> through the company server, except for a couple of issues.

Fair enough

> First off, I also need to enable STARTTLS in order not to have
> passwords transmitted in clear-text over the wire.  However, STARTTLS
> appears to require a certificate on the client side, and self-signed
> client side certificates don't seem to work, especially with Outlook

The server can send a self-signed certificate, which the client has to accept
ONCE and declare a valid / trusted certificate.

> Secondly, is there any way to tell sendmail that if, e.g user ``raju''
> logs in using SMTP AUTH then it should only relay messages which come
> from that client AND which have ``[EMAIL PROTECTED]'' as the sender

Any particular reason for this?  Once someone AUTHs himself, only his IP can
relay through your server for a short window of time.  If it really matters
what the envelope-from should be, you might try Jan Krueger's site at 
http://www.digitalanswers.org/check_local for ideas.

> address?  In other words, even with SMTP AUTH enabled the sender can
> choose any envelope sender and make the message appear to be from
> another person.

Feature of [E]SMTP.  Not very necessary to limit this - especially as people
might well have other email addresses forwarding to their account.

> mail recipients aren't clued in enough to be able to figure out what a
> signature is or distinguish a good signature from a bad one, so we
> need to be able to configure Sendmail to check and reject messages
> with forged envelopes.

It is very trivial to get around such checks - and even to forge valid
envelope froms.  

Thawte / Verisign certificates are built into OE - or there are some
excellent PGP clients for windows, which integrate rather well into outlook.

Training your users might be the best thing to do :)

-- 
Suresh Ramasubramanian  <---->  mallet <at> efn dot org
EMail Sturmbannfuhrer, Lower Middle Class Unix Sysadmin

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