Thanks to everyone for the replies. Yes I see now that it would cause problems with mailing lists... I know how to block specific domains, but the shear volume of domains that sends junk mail makes that unmanageable (Apart from the fact that we also get legitimate mail from some of those domains). Steve's method of stopping people from spoofing his own domain sounds like something I could use. I will look into implementing that in SendMail (any info on how to do this would be appreciated). Our SMTP server requires authentication, so I should be able to set it up exactly as Steve has (assuming SendMail is capable of this). Thanks again for all your help. Donald Tyler -----Original Message----- From: redhat-list-bounces@xxxxxxxxxx [mailto:redhat-list-bounces@xxxxxxxxxx] On Behalf Of Cowles, Steve Sent: Tuesday, July 20, 2004 10:04 AM To: 'General Red Hat Linux discussion list' Subject: RE: configuring sendmail to reject spoofed email addresses Donald Tyler wrote: > Hi, > > Like everyone else, our junkmail is getting horrendous. Most of the > emails we receive use an email for the "From" section of the header, > but it doesn't match the email in the "Return-Path" section. > > My question is this: > > Is there anyway to configure sendmail so that if there is an email > address in the "From" section, and it does not match the > "Return-Path" section, for it to reject the email? > > Thanks in advance > > > Donald Tyler Donald, First, I no longer use sendmail as my MTA, so I can't answer your question directly. I now use postfix. Second, if I understand your post correctly, you are wanting to configure sendmail to test against the "Return-Path" header. According to RFC-822, this particular header entry is added by the LDA (like procmail), not sendmail. Third, So that you can ask your question using terminology that everyone will understand, look at the following sections of an e-mail... Basically an e-mail is broken up into envelope, header and body sections. # telnet mail.mydomain.com 25 220 mail.mydomain.com ESMTP Postfix (2.1.1) --> Start of envelope helo mail.remote_mta.com 250 mail.mydomain.com mail from: <scowles@xxxxxxxxxxxx> --> envelope from 250 Ok rcpt to: <scowles@xxxxxxxxxxxx> --> envelope to 554 <scowles@xxxxxxxxxxxx>: Envelope address rejected, Go Away! rset --> Lets start over 250 Ok mail from: <steve_cowles@xxxxxxxxx> --> envelope from 250 Ok rcpt to: <scowles@xxxxxxxxxxxx> --> envelope to 250 Ok data --> End envelope, start header 354 End data with <CR><LF>.<CR><LF> From: Steve Cowles <steve_cowles@xxxxxxxxx> --> Header from To: Steve Cowles <scowles@xxxxxxxxxxxx> --> Header to Subject: This is a test. --> Header subject --> Blank line, end header, start body This is line 1 of body. This is line 2 of body. . --> End body, submit to defined mailer 250 Ok: queued as ADAF839CA quit 221 Bye Note the 554 reject line 554 <scowles@xxxxxxxxxxxx>: Envelope address rejected, Go Away! I have postfix configured to reject anyone claiming to be from mydomain.com when specified as the envelope from address, not the header from. Is this possibly what your wanting sendmail to test? BTW: If I was to test the header from for mydomain.com, then I could no longer accept e-mail from the redhat list servers. Check the headers of this e-mail. Hopefully the above will help you understand exactly what you want to test and give you some pointers on where to implement this in sendmail. If I remember right, the /etc/mail/access file tests the envelope from/to addresses. i.e. mydomain.com REJECT This is basically how I configure postfix, but I also have to allow SMTP AUTH clients to specify an envelope sender being from mydomain.com. Fortunately, postfix works on the basis of the "First Test Wins" methodolgy. So the ordering of my tests is critical. Steve Cowles -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list
