Backscatter solutions

[Jo Rhett]

On May 9, 2008, at 6:15 AM, Joseph Brennan wrote:
> Forget SPF.  Why should any system accept mail for an unknown  
> recipient
> and then mail a bounce?  That's the primary cause of backscatter.   
> These
> systems are just as likely to accept the message, then check SPF, and
> mail a bounce :-)

There are a number of different systems that try to be smart about  
when to send back a bounce message.  Pretty much every MLM besides  
Mailman includes logic attempting to return valid syntax errors to  
senders, but avoid backscattering people.   SPF is obviously part of  
that equation.

And it does help fairly significantly in practice.  We have some wide  
open/non-filtered mailboxes that we are required to run.   
Implementing SPF on those mailboxes reduced our backscatter by about  
24% instantly, which was just under 500 messages a day.

-- 
Jo Rhett
Net Consonance : consonant endings by net philanthropy, open source  
and other randomness