From: Paul M Foster

> Regarding the rejection of dynamic IPs by smarthosts, are you saying
> that it's a "blacklist" of sorts that lets them know an IP is dynamic?
> (Serious question. I don't know the mechanism by which they determine
> what is and isn't a dynamic IP.)

You are talking about two different mechanisms here. The black or grey
lists are services that track known open relays and other sources of
spam, viruses and assorted malware. Anyone can subscribe to them and use
them to validate relay requests.

There are also services that keep track of valid domain addresses and
the IP assigned to them. They are usually called DNS hosts. These can be
polled to identify the IP address for authorized domains and hosts.
There are even special records for the email severs within a domain.
Most dynamically allocated IP addresses will not show up on these
servers unless you have access to a service authorized to inject

So basically, qmail did a DNS lookup on your host/domain name and did
not find a record pointing to your server. Therefore it rejected your

You will have to ask your ISP for the address of their SMTP and POP
servers if you don't know them. But usually your email client is already
configured to talk to them. I would just go into my Thunderbird setup
and look up those addresses.

Bob McConnell

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