Anyone using

Jim Holland mailscanner at
Wed Sep 6 23:07:28 IST 2006

On Thu, 7 Sep 2006, Res wrote:

> On Wed, 6 Sep 2006, Jim Holland wrote:
> > On Thu, 7 Sep 2006, Res wrote:
> >
> >>> Actually I had the most trouble with foward and reverse DNS. I turned
> >>> that off because my whitelist had grown to over a couple hundred
> >>> entries. With greylisting I've only had to add 5 or 6 domains.
> >>
> >> the vast majority of failed attempts come from no PTR's and those that
> >> dont have them, tends to indicate lazy network admins so i wouldnt expect
> >> them to take action on spammers either, I simply whitelisted
> >> in sendmail and qmail and alls been happy since, AOL also still do this i
> >> understand, so the collateral damage cant be all that bad if tehy still do
> >> it :)
> >
> > I use the RDNS etc checks as a kind of poor man's greylisting - I give a
> > 451 to all errors and then let them try again at our higher MX.  That
> > minimises the need to do whitelisting.
> I can see that idea working well with no overheads.
> You ever had hotmail try your secondary MX ?
> Once had a disk fail, it was down for only 20 minutes in total time, 
> hotmail couldnt connect and rejected the msg to the sender, I tested this 
> out for myself in the early hours of the following morning by killing 
> sendmail for a couple mins, i got a reject msg back within 2 mins from 
> hotmail, i thought it weird and hope it was only a temp misconfig.

I haven't noticed hotmail doing that, but other large ISPs such as Yahoo, 
Gmail, MessageLabs etc seem to make only a single delivery attempt and if 
that tempfails they still return the mail to sender and don't try the 
secondary.  Very annoying!


Jim Holland
System Administrator
MANGO - Zimbabwe's non-profit e-mail service

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