Security Basics mailing list archives
Re: educating rDNS violators
From: Derek Schaible <dschaible () cssiinc com>
Date: Wed, 25 Aug 2004 14:20:25 -0400
On Wed, 2004-08-25 at 13:55, someone wrote:
This becomes even further complicated if a company is hosting with somebody who provides "virtual domain" mail hosting. The server could be mail.somefamily.net, but have a reverse DNS entry that points to mail.myprovider.net. How is that invalid? Just because the records don't match doesn't make me a spammer!
Mail servers should have correct DNS info. Forward and reverse. It is the sysadmin's responsibility to ensure that their systems are configured properly. Period.
I wanted to respond to this point to the list before I get flooded with similar replies. True, such a situation does not make you a spammer but using a virtual domain will in no way impact the reverse DNS of the smtp server from which the email is delivered. Reverse DNS is not matching the address of the smtp server to the domain name in the email address. This would break many things like reply-to, etc. All it is doing is verifying that the server is who it claims to be. Virtual mail domains are not impacted. I run many virtual email domains as well for every website we host. These accounts can happily send mail through our company's SMTP server, arrive in tact and survive an rDNS lookup. As I've stated earlier, filtering out mail from servers with a bad rDNS will dramatically reduce your spam and that's a fact to live by. There is always a means in which you can configure a valid email system that will pass this test. Some require more imagination than others, but it can always be done and should always be done if you want to guarantee that your mail will be delivered and not rejected. -- Derek Schaible <dschaible () cssiinc com> CSSI, Inc.
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Current thread:
- educating rDNS violators SMiller (Aug 23)
- Re: educating rDNS violators token (Aug 24)
- Re: educating rDNS violators Derek Schaible (Aug 25)
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- Re: educating rDNS violators Derek Schaible (Aug 25)
- RE: educating rDNS violators David Gillett (Aug 26)
- Re: educating rDNS violators token (Aug 26)
- RE: educating rDNS violators David Gillett (Aug 30)
- Re: educating rDNS violators Derek Schaible (Aug 25)
- Re: educating rDNS violators token (Aug 24)
- Re: educating rDNS violators Niek (Aug 26)
- Re: educating rDNS violators Derek Schaible (Aug 30)
- Re: educating rDNS violators James Kelly (Aug 25)
- Re: educating rDNS violators Bryan S. Sampsel (Aug 25)
- Re: educating rDNS violators SMiller (Aug 26)
- Re: educating rDNS violators Derek Schaible (Aug 25)