Re: [cobalt-users] Can someone point me to sendmail configuration I read here before...

[Jeff Lasman <blists@xxxxxxxxxxxxx>]

On Friday 12 December 2003 05:27 am, Greg Hewitt-Long wrote:

> Ages ago I read on this groups how to configure the RAQ servers to
> only accept email from servers with valid reverse lookups - this cut
> down the amount of spam enormously - the only problem, I can't
> remember how it was done, and I can't find the old post among the
> enormous amount of related posts to the group... pointer gratefully
> accepted!

It's a great idea, in theory.  Before you implement it check your own 
RaQs to make sure you have reverse DNS implemented properly.  My 
experience is that if you implement reverse DNS according to the 
instructions that came with your RaQ, unless you've lucked out on your 
provider, or taken additional steps, you may not have reverse DNS 
thought you think you do.

For example, the domain in your return address resolves to an IP that 
does NOT have reverse DNS.

Do you want others to implement this as well, and not be able to get 
email from your mailserver?  

Note that many quite legitimate mailservers don't have reverse DNS 
entries, some by error and some by design, and that there's no RFC 
requirement that reverse DNS be implemented.  One RFC actually says "be 
conservative in what you send and liberal in what you receive".  Why 
that may not be a great idea on today's Internet, until and unless more 
mailservers are properly configured to resolve properly configured 
reverse DNS, I think it a bad idea.

You might lose lots of non-spam email as well.

Jeff
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