The usual reason for anti-spam programs to reject an address such as yours is that it is assigned dynamically, so at any given moment, there is no way to know what host is using it. The spamming opportunity that dynamic assignment offers is most apparent with dial-up accounts, but it applies to dynamic assignment methods like DHCP and PPPoE as well. May ISPs provide (or the anti-spammers otherwise acquire) lists of their dynamically-assigned IP addresses, and the anti-spam programs offer that as one possible blackhole list (a different one from the "known open relay" list ... the well-known one is the DUL or dial-up list).
The antispammers take the position that people with dynamic IP addresses should be forced to use their ISPs' mail relays. Those smarthost relays, if properly configured, will allow outgoing mail only from authorized, authenticated users (and if not properly configured, will be on the open-relay list so blocked).
The only saving grace here is that not many sites use the DUL to block e-mail, possibly because it is somewhat inaccurate (my static address, for example, occasionally turns up on it), possibly because enough legitimate users have setups like yours that using it blocks too much non-spam e-mail.
So ... the context in which use of smtp_auth comes up is that it is a device for authenticating your outgoing mail to your ISP for forwarding by its mail forwarder (relay). The details here can vary a bit from ISP to ISP, but one common mechanism is to require POP3 authentication (userid and password, called POP before SMTP) before accepting e-mail for relaying. There are also several SMTP-specific methods around, but I do not know how often any of them is actually used.
The standard implementation of smtp_auth in Linux MTAs does not appear to handle this problem. It handles the other side of the problem ... that is, it provides a way for you to require that your users authenticate themselves before they are able to send mail. Its most important use (I think) is to allow your offsite users with dynamic addresses (mobile users, DHCP users, PPPoE and dial-up users) to use your SMTP server as a relay.
Unfortunately, after a bit of looking, I could find no indication that either sendmail or any of the other common Linux MTAs (exim, postfix) implements a way to authenticate itself to a smarthost relay. I did find this reference to a sendmail *variant* that provides client-side smtp_auth in SuSE --
http://sdb.suse.de/en/sdb/html/sendmail_smtp_auth.html
I also found a reference to an MTA called Masqmail that seems designed to do what you want --
http://innominate.org/kurth/masqmail/
Finally, this site lists a bouch of MTA alternatives, but of them, only the two I mention above looked promising for your situation --
http://www.linuxlinks.com/Software/System/Daemons/SMTP/index.shtml
In closing, I am sorry that this is not the sort of direct, focused help you wanted. I hope it will still be of some use to you. Good luck.
At 10:21 AM 11/28/02 +0100, Theo. Sean Schulze wrote:
Hello,
Does anyone have any advice they can offer on setting up smtp_auth on my SuSE 8.0 system at home? The problem I am trying to solve is this. My SuSE 8.0 system here at home (dragoon.nuthole.de/localhost) is set up to send my emails out as [EMAIL PROTECTED] Teamfinders.org is a domain that I have that is hosted by a hosting service, and that service is not my ISP. My ISP is 1&1 here in Germany, and I have a separate domain there that they offered as part of my DSL package. Several times now I have gotten email deliveries rejected because the dynamically assigned IP I receive from 1&1 is blackholed. There appears to possibly be an issue with the machines at those addresses being open relays used for spamming. I have checked my mail logs, and as far as I can tell, my machine is rejecting attempts to use it as an open relay. Several of the rejection messages have suggested the possibility that the emails would have been accepted if I had been using smtp_auth.
I have read through SuSE's configuration file at /etc/sysconfig/sendmail, and shortly I will start working my way through /usr/share/doc/packages/sendmail/README and /usr/share/doc/packages/sendmail/op.txt.bz2. I have also printed out several articles from www.sendmail.org/~ca/ and have begun to read through those. (That's going to take several re-reads though before I've grokked all that.) So, I have no shortage of information on the topic. What I was hoping for was that if anyone on the list has some helpful hints or tips from having done something like this himself, particularly setting up a home server to climb out of the black hole, then that might help me get a step ahead.
-- -------------------------------------------"Never tell me the odds!"-------- Ray Olszewski -- Han Solo Palo Alto, California, USA [EMAIL PROTECTED] ------------------------------------------------------------------------------- - To unsubscribe from this list: send the line "unsubscribe linux-newbie" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs
