Since almost all spam I receive are comming from dynamic or dialup IP's I've been thinking of a filter function that might be useful.
If the rDNS lookup contains digits which matches the IP number the attempt would be rejected. An option could be how many digits that has to mach for rejection.
Mail filtering
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We've added an option to Client Validity Checks (under Handling Options) called "Reject 'dynamic' Client Hostnames" that looks for common substrings of the IP address in the reverse DNS name. If any of these are found, the message is rejected. There are two modes for this option: Basic and Advanced.
Basic mode contains the full IP address with various common separators in forward and reverse format. For example, the IP a.b.c.d would have the basic patterns:
a.b.c.d
d.c.b.a
a-b-c-d
d-c-b-a
abcd
dcba
Advanced currently contains one additional pattern:
bd
We will add more patterns to advanced mode as we see them or as they are suggested to us.
Basic mode contains the full IP address with various common separators in forward and reverse format. For example, the IP a.b.c.d would have the basic patterns:
a.b.c.d
d.c.b.a
a-b-c-d
d-c-b-a
abcd
dcba
Advanced currently contains one additional pattern:
bd
We will add more patterns to advanced mode as we see them or as they are suggested to us.
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Roller Network LLC
Roller Network LLC