email being rejected by one foreign ISP

[Mark_Andrews at isc.org]

> I am trying to send a email to someone in Europe. I get an error
> message back:
> 
> <username at isp.net> host example.machine.isp.net[xxx.xxx.xxx.xxx]
> refused to talk to me: 554 SMTP service not available (failed to find
> a hostname from ip address
> 
> 
> The problem does not happen if I send the message using my static IP
> address. It only bounces with dynamic IP's to this particular domain.

	Well the simple fix is to ensure that there is a PTR record
	with a corresponding A records in the DNS for the dynamic
	address.

	You could also try to get the dynamic address range white
	listed.

	The ISP is using a "clue filter" to try to stop spam.  The
	clue here is to know how to setup the dynamic range so it
	has a valid PTR/A pair or to switch to a ISP that has the
	clue to do so.

	A stricter clue filter also requires that the PTR match the
	name in the HELO / EHLO of the SMTP exhange.  This requires
	dynamic DNS support in whatever is handing out the addresses
	and maybe the host as well.

	Mark
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at isc.org