Re: People forging their From: addresses

[Ulf Vedenbrant <]

> For a while, I tried returning a 500 code, but I found that the DNS
> is flaky enough to actually provide false answers now and then, so I
> ended up rejecting a few messages a day who were otherwise perfectly
> legal (out of like oh 100k per day).
> 
> So we switched back to 400 replies, so now the occasional mail gets
> delayed a bit because it gets an "unfair" 400 reply, but that's
> better than rejecting that mail altogether. Spammers will usually
> not retry even with 400 style replies when they're sending directly,
> and relays stop after a few days... it's bearable.
> 

For those mails the delay normally would indicate a malfunctioning
dns server. At least that is my experience. We have been running
sender domain checkup for a year or so and it really kills a lot
of junk mail..

/Uffe