Wow. What an explanation. Thank you! If I understand right a problem can ocur if one of our clients mailservers (most of them exchange servers) become a open relay because the admin has changed something. If this server has set our Imail-Server as smarthost and uses SMTP-Auth to deliver the messages a "percent hack" can use our server to relay.
Markus > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]] On Behalf Of > Smart Business Lists > Sent: Monday, January 27, 2003 12:12 PM > To: Markus Gufler > Subject: Re: [Declude.JunkMail] PERCENT test > > > Markus, > > Monday, January 27, 2003 you wrote: > MG> How can I test relaying trough my servers using the %piggyback > MG> address? "[EMAIL PROTECTED]" should be the > MG> correct format. This will not work. > > You have 2 mail servers, example.com, which is an IMAIL server, > and example.net. Example.net lives on a different network, backs > up example.com, and may or may not be an IMAIL server. I will > discuss below how to relay mail to a third domain, example.org, > using the %piggyback technique: > > Example.net is a backup for example.com. The Admin who runs > example.com mistakenly entered the IP address of example.net > in his allowed to relay ACL. Or perhaps he runs both servers > and has each backup the other. > > So send a message addressed to "[EMAIL PROTECTED]" > through the example.net server (the backup server for > example.com). > > Since example.net is a backup for example.com it inspects the > message and correctly accepts it for delivery to example.com > which is the correct domain parsed from the address. The > message is queued and sent on to example.com. > > When example.com, our IMAIL server, receives the message it > checks to see if example.net is authorized to relay. If it is > then IMAIL parses the address in such a way that the % sign is > changed to an @ character and delivery is attempted to > [EMAIL PROTECTED] In part this is because the % > sign (and > other characters can be used as a domain delimiter. > > In fact neither server has done anything really wrong. But > the effect of the process is that you will be listed as an > open relay if you are tested in this way. > > The obvious solution is to make certain you do not allow > relaying for any backup mail servers. > > And if that is not possible then you have to rely on Declude's > PERCENT test. > > MG> What can Scott mean by writing "IMail does normally check > for this, > MG> but there is a report of it not catching this type of mail under > MG> certain circumstances." ? > > Just exactly what it says. > > IMAIL and other mail servers can be set to use other domain > delimiters besides the "@" character. There are actually valid > uses for this phenomenon, too. It dates back to early sendmail or > perhaps even earlier. > > hth > > Terry Fritts > > --- > [This E-mail was scanned for viruses by Declude Virus (http://www.declude.com)] --- This E-mail came from the Declude.JunkMail mailing list. To unsubscribe, just send an E-mail to [EMAIL PROTECTED], and type "unsubscribe Declude.JunkMail". The archives can be found at http://www.mail-archive.com. --- [This E-mail was scanned for viruses by Declude Virus (http://www.declude.com)] --- This E-mail came from the Declude.JunkMail mailing list. To unsubscribe, just send an E-mail to [EMAIL PROTECTED], and type "unsubscribe Declude.JunkMail". The archives can be found at http://www.mail-archive.com.
