Milter-greylist

--- In milter-greylist@yahoogroups.com, Oliver Fromme <olli@...> wrote:

>  > 
>  > What version of milter-greylist are you running?
> 
> I think the correct question to ask would be: What OS are
> you running?  :-)
> 
> Milter-greylist uses the regex functions from the libc of
> the OS.  So if those functions are broken (or use a syntax
> different from other systems), then that will also affect
> milter-greylist's usage of regular expressions.

Good point, thank you!

> 
> Furthermore, a lot of internet access providers use the
> hexadecimal IP (instead of decimal) for the reverse look-
> up of their pools.  So it's probably a good idea to add
> a similar regular expression that matches IP addresses
> expressed in hexadecimal, for example:
> 
> [0-9a-f]{2,2}[-.]?[0-9a-f]{2,2}[-.]?[0-9a-f]{2,2}[-.]?[0-9a-f]{2,2}
> 
> (Note that milter-greylist uses case-insensitive matches,
> so it's not necessary to say "[0-9A-Za-z]".)
> 
> That will match things like 5f-8b-23-cd.dsl.example.com,
> 5f8b23cd.cable.foo.net, and even 5f-8b.23-cd.dyn.bar.org
> or 5f8b-23cd.pool.baz.biz.

Unfortunately, it will also match web307045.mail.mud.yahoo.com, which
is a very valid mailer. In order to reliably detect hex addresses
without separators, you'd need two passes of regexes: the first to
identify a string of 8 hex numbers, and then a second one to make sure
there is at least one non-decimal number in that string. I don't think
this is possible with milter-greylist at this time.

The good news is that this combination is not very common, and leaving
it out of the regex does not significantly affect the hit rate.