ISPs blocking SMTP connections from dynamic IP address space

Bruce Pea pea at
Thu Aug 7 05:49:53 PDT 2003

Since we began blocking servers with no reverse DNS we've been amazed at 
how many mail servers are setup with no reverse DNS. We've had several 
instances where we've been asked by the party being blocked how to fix 
the problem. Since I'm not a DNS expert all I've been able to tell them 
is to fix their DNS entry so they show up when we do an nslookup on them, 
which isn't very helpful but is about all I know to say.

It would be very useful if someone could explain or give instructions on 
how to fix this problem so we all could pass the info along to people who 
need to straighten out their DNS.

Does anyone have a document explaining such things handy they could 


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