No need to give them a buzz, they aren't blocking on that criteria. A quick test reveals that SBC does not block if the ehlo string does not match the rDNS record. They do however block addresses they determine to be dynamic.
There's more than one way to determine that. Some people use a regex to determine that based on the PTR of connecting host. In this case dsl.*.swbell.net is probably sufficient to kick off that filter. A PTR of some.host.other.than.what.i.ehlo.com would probably not result in a rejection. If SBC or some other host is using netblocks to determine their filtering, whether or not my PTR matches my EHLO is also not relevant as the netblock of my server does not change. If they were blocking on this criteria I'd need either a static IP or to relay though a smart host. My PTR/EHLO parings aren't a factor. > set q=mx > sbc.com Server: dns1.austtx.sbcglobal.net Address: 151.164.20.201 Non-authoritative answer: sbc.com MX preference = 50, mail exchanger = tspsmtp8b.sbc.com sbc.com MX preference = 60, mail exchanger = sbcsmtp5.sbc.com sbc.com MX preference = 70, mail exchanger = sbcsmtp3.sbc.com sbc.com MX preference = 40, mail exchanger = sbcsmtp1.sbc.com sbc.com MX preference = 40, mail exchanger = sbcsmtp2.sbc.com 220 sbcsmtp2.sbc.com ESMTP Thu, 1 Jul 2004 17:45:07 -0500 (CDT) ehlo clownpenis.fart 250-sbcsmtp2.sbc.com Hello adsl-68-92-150-59.dsl.austtx.swbell.net [68.92.150.59 ], pleased to meet you 250 ENHANCEDSTATUSCODES mail from: [EMAIL PROTECTED] 550 5.0.0 SBCIS Dynamic IP - Access denied > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:bounce- > [EMAIL PROTECTED] On Behalf Of Tim Vander Kooi > Posted At: Thursday, July 01, 2004 5:10 PM > Posted To: swynk > Conversation: MX records and Reverse DNS lookup > Subject: RE: MX records and Reverse DNS lookup > > Feel free to give SBC a buzz and give 'em a piece of your mind. I'm not in > favor of the rule...simply letting the person who started the thread know > what the new rules are for some ISPs. We're all allowed to not like the > rules all we want, we still have to play by them as long as they exist. > > -----Original Message----- > From: Chris Scharff [mailto:[EMAIL PROTECTED] > Sent: Thursday, July 01, 2004 4:52 PM > To: Exchange Discussions > Subject: RE: MX records and Reverse DNS lookup > > > An rDNS entry isn't needed to figure out who is responsible for a > particular IP address. It's also non-RFC compliant. > http://www.rfc-ignorant.com/ ought to add a category for hosts which > reject mail as a result. > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Tim > Vander Kooi > Posted At: Thursday, July 01, 2004 2:44 PM > Posted To: swynk > Conversation: MX records and Reverse DNS lookup > Subject: RE: MX records and Reverse DNS lookup > > It will stop all the "make $0.25 working from home by sending out spam" > spammers, because they have no control over their rDNS records. It also > now provides a level of "trackability" to the message. As a recipient, I > now know where the message originated. I can complain to the ISP > providing the spammers service, and with enough people being vocal about > it the ISP can shut them down. > > -----Original Message----- > From: Ken Cornetet [mailto:[EMAIL PROTECTED] > Sent: Thursday, July 01, 2004 1:48 PM > To: Exchange Discussions > Subject: RE: MX records and Reverse DNS lookup > > > No, it isn't simple if you have multiple outbound SMTP servers that are > being NAT'ed through one IP address. > > Besides, this check won't stop spam. As soon as this check becomes > common-place, spammers (and spam zombies) will just start sending the > "correct" HELO string. > > Our SMTP HELO host does not match the reverse lookup of the public IP > address of our firewall, and I only have about 1 problem site per year. > A quick conversation with the site admin usually reveals that they are > getting lots of complaints about reject email from many domains. As soon > as I point out that they are not RFC2821 compliant, they remove the > check. > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Tim > Vander Kooi > Sent: Thursday, July 01, 2004 11:55 AM > To: Exchange Discussions > Subject: RE: MX records and Reverse DNS lookup > > > SBD does it now. So if you have yours setup in a way that doesn't > conform you're going to start having a good sized chunk of mail not > reach it's intended recipient. And it's just going to get worse over > time. It's very simple to set an rDNS entry that matches your HELO > though, so I'm not sure it's a huge deal. Just something that all > Exchange and Network admins need to be aware of. > > -----Original Message----- > From: Ken Cornetet [mailto:[EMAIL PROTECTED] > Sent: Thursday, July 01, 2004 11:37 AM > To: Exchange Discussions > Subject: RE: MX records and Reverse DNS lookup > > > To all who consider rejecting an SMTP connection based on what's in the > HELO command, you WILL start rejecting valid email: > > If you reject connections based on no PTR record for the connecting IP, > you will reject a little valid email. If you reject based on the PTR > record not matching the host name in the HELO, you will reject a lot of > valid email. > > Thus the prophets spoke in RFC2821 verse 4.1.4 > > An SMTP server MAY verify that the domain name parameter in the EHLO > command actually corresponds to the IP address of the client. > However, the server MUST NOT refuse to accept a message for this > reason if the verification fails: the information about verification > failure is for logging and tracing only. > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jim > Kennedy > Sent: Thursday, July 01, 2004 10:54 AM > To: Exchange Discussions > Subject: RE: MX records and Reverse DNS lookup > > > > What most of them are doing is looking at the PTR record of the sending > IP and compare it to what you announce in your HELO. And making sure > they match. They do this because it is very effective at weeding out > zombied machines. The SMTP HELO of the infected machine is not going to > match the PTR of the IP. > > What they are doing is suggested by the RFC's, but not required. > > So this is an easy fix for you. Just look at the PTR of each of your > public IP addresses that your email servers use. Then go into Exchange > and adjust the HELO to match. Hopefully you have exchange 2003, it is a > really easy fix. It is in the SMTP properties as 'masquerade domain' > > JK > > > > -----Original Message----- > From: On Behalf Of April Fleming > Subject: MX records and Reverse DNS lookup > > It is my understanding that many email servers will do a reverse dns > lookup on incoming email to ensure a valid domain when sifting out spam > etc. > > Thus, I must ensure that my email server which is sending out email must > have an MX record so the Reverse DNS lookup will suceed. > > What I would like to know is whether the weight given the MX record will > affect the reverse dns lookup. If I have email being sent from email > server 3 (don't ask why, it isn't the point :) and that email server is > weighted 15, will the email servers I am sending out to accept the > email? > > Example > > MX 5 Email server 1 > MX 10 Email server 2 > MX 15 Email server 3 > > Thank you! > > April > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&; > lang=english > To unsubscribe send a blank email to > %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&; > lang=english > To unsubscribe send a blank email to %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&; > lang=english > To unsubscribe send a blank email to > %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&; > lang=english > To unsubscribe send a blank email to %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: > Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&; > lang=english > To unsubscribe send a blank email to > %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: > Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: http://intm-dl.sparklist.com/cgi- > bin/lyris.pl?enter=exchange&text_mode=&lang=english > To unsubscribe send a blank email to %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: > Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: http://intm-dl.sparklist.com/cgi- > bin/lyris.pl?enter=exchange&text_mode=&lang=english > To unsubscribe send a blank email to [EMAIL PROTECTED] > dl.sparklist.com > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: > Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Web Interface: http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&lang=english To unsubscribe send a blank email to [EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. 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