++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++ sendmail-unknown-domain-FAQ.txt ++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Tue, 17 Mar 1998 16:11:22 +0100 (MET) From: Leif Erlingsson To: Dwight Johnson Subject: Re: Sendmail Relay Question On Mon, 16 Mar 1998, Dwight Johnson wrote: > Hi Leif, > > I know you are a sendmail expert. > > Normally, sendmail on my system simply contacts the destination > mailserver directly. Sometimes, however, my mail is rejected > because I have a dial-up Internet connection and the recipient > mailserver has rules in place to reject mail unless it comes > from a registered IP address. > > To correct the above, I would like to configure sendmail to > simply request an SMTP relay through the mailserver of my > domain hosting service. > > How do I do that? > > Thanks in advance, > Dwight My ISP have all his IP's registered, see these three sample Received headers: Received: from elijah.swip.net (dialup172-1-22.swipnet.se [130.244.172.22]) Received: from default (dialup113-1-30.swipnet.se [130.244.113.30]) Received: from elijah.swip.net (popmail@dialup237-2-2.swipnet.se [130.244.237.66]) (the first is from my own system, the second is from a Win-95 user -- Microsoft Internet Mail 4.70.1155 -- on the same ISP) In your mail the IP [209.43.157.175] might for example be registered as dialup157-3-47.accessone.com [209.43.157.175] My ISP is using a 26-bit subnet-mask; 255.255.255.192, and these domain names for the dynamic dial-in IP's: dialup{N3}-1-{1..60}.swipnet.se [130.244.{N3}.{1..60}] dialup{N3}-2-{1..60}.swipnet.se [130.244.{N3}.{65..124}] dialup{N3}-3-{1..60}.swipnet.se [130.244.{N3}.{129..188}] dialup{N3}-4-{1..60}.swipnet.se [130.244.{N3}.{172..252}] Where {N3} is one of these: {112..123,144..187,200..211,232..239} (Determined using dig repetitively... ;-).) If your ISP would adopt a similar scheme, it might look like so: dialup{N3}-1-{1..60}.accessone.com [209.43.{N3}.{1..60}] dialup{N3}-2-{1..60}.accessone.com [209.43.{N3}.{65..124}] dialup{N3}-3-{1..60}.accessone.com [209.43.{N3}.{129..188}] dialup{N3}-4-{1..60}.accessone.com [209.43.{N3}.{172..252}] Where {N3} is: {157, or any other value used by your ISP} If and when you fail to influence your ISP to do this trivial change to his DNS, you can either change ISP or indeed update your sendmail.cf. If you are using m4 source (recommended), simply add define(`SMART_HOST', `smtp:mailhost.accessone.com')dnl to your sendmail.mc file and make sure your LOCAL_NET_CONFIG section, if you have one, doesn't send directly to things found in your DNS lookup (mine does, I wrote it myself). Then run m4 on it; m4 < sendmail.mc > /tmp/new-sendmail.cf Then diff /tmp/new-sendmail.cf /etc/sendmail.cf before replacing, just to see what changed. This ought to work! (Myself, I only forward stuff to my ISP if I cannot find the domain in DNS on the assumption that my ISP knows better -- which he never does. :-)) You can study my files at ftp://www.lege.com/www.lege.com/sendmail/cf-8.8.8/... Look for elijah* and proto.m4, and also ruth* files. Ruth is a null-client to elijah. Good Luck! __________________________________________________________________ Leif Erlingsson, DATA LEGE, Glavagatan 33, 123 71 Farsta, Sweden. TEL +46 8 604-0995, FAX +46 8 605-2551, URL http://www.lege.com. I remember the past. I am not doomed to buy Microsoft products. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++ END OF sendmail-unknown-domain-FAQ.txt ++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++