Man, they'll try anything to hack your system...

[Dan Jenkins]

Bill McGonigle wrote:

> Now that you mention it, I've seen few in the past few days with no MX 
> records for the sending domain, even with a PTR record for the sending 
> host.  Not the same, but similarly strange and recent.
>
> I'd be happy to add a SpamAssassin or postfix rule to ignore mail from 
> senders with no reachable MX for a reply.
>
> All that said, somebody might have just messed up their BIND views.

A few years ago a client asked me to block more junk mail. I restricted 
based on lack of a MX record. Eight out of fourteen board members could 
no longer send email to the organization. (Three of them were technology 
companies, no less.) I haven't tightened things down since then. ;-)

I keep wanting to, but my clients are concerned about not getting 
legitimate emails, even though they also want to reduce junk.

What experience have folk had tightening restrictions, like lack of MX 
or A or mis-matched MX/PTR pair?
Does it still cause a lot of false rejections?

-- 
Dan Jenkins (dan at rastech.com)
Rastech Inc., Bedford, NH, USA --- 1-603-206-9951
*** Technical Support Excellence for over a quarter century