North American Network Operators Group

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Re: email issues?

  • From: Sean Donelan
  • Date: Fri Jan 24 19:20:51 2003

>   Rejecting on broken or non-existing DNS will probably reject mail from
>   more than 15% of all mail servers on the Internet - guaranteeing a
>   false positive rate not even matched by the combined 6 DNSBL's I
>   use - cumulative and with hard 5xx rejects. AT&T on the other hand,
>   will use DNSBL's when the first snowball emerges from hell unscathed.

In the good old days, when network engineers used VT100 terminals and 300
baud (not bps) acoustic modems, enforced the requirement for
"valid" reverse and forward DNS entries for anonymous FTP access.  It was
sometimes the only way I could convince customers to type the line in both
DNS files.  If you don't have valid Address<>Name mappings, you won't be
able to download files from

Doesn't anyone else find it funny when people scream that ISPs should
block ports and shoot people with misconfigured systems; yet when
an ISP actually does enforce even a modest requirement; people start
screaming how unfair or stupid that ISP is for doing that.