The 5.5 IMS performs reverse lookups by default and can be disabled with a reg tweak.. E2k does not by default, but can be enabled to do so. Neither 5.5 nor E2k disconnect sessions if the domain does not resolve correctly - in otherwords, the reverse lookup is not designed to prevent SPAM but rather to simply place the resolved name in the message header. Reverse Lookups can cause performance degradation.
-----Original Message----- From: Pfefferkorn, Pete (PFEFFEPE) [mailto:[EMAIL PROTECTED]] Sent: Friday, July 12, 2002 2:38 PM To: Exchange Discussions Subject: Reverse DNS and Exchange Exchange 5.5 I'm a little confused on Reverse DNS. I kind of understand the concept that with Reverse DNS enabled the Mail from: entry must resolve to a valid domain or it will get rejected. Some I have some basic questions: I take it Exchange 5.5 does not support Reverse DNS? How about Exchange 2000? How effective is Reverse DNS to help the control of Spam? What problems/issues will we encounter if we do implement reverse DNS in some for on front end servers whatever it may be? What about users who have POP and have their return address set to be something other than their ISP but they use the ISP as the relay? When they state the Mail From: they mean the From: in the display area and not all the routes? If you have a front end relay like PMDF/VMS which relays first.last@domain to a messaging system, reverse DNS will not prevent spam to the receiving systems since it will also validate from the relay? Pete Pfefferkorn Senior Systems Engineer/Mail Administrator University of Cincinnati 51 Goodman Street Cincinnati, OH 45221 Phone - (513) 556-9076 Fax - (513) 556-2042 _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] ------------------------------------------------------------------------------ The information contained in this email message is privileged and confidential information intended only for the use of the individual or entity to whom it is addressed. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copy of this message is strictly prohibited. If you have received this email in error, please immediately notify Veronis Suhler Stevenson by telephone (212)935-4990, fax (212)381-8168, or email ([EMAIL PROTECTED]) and delete the message. Thank you. ============================================================================== _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED]
