OT: Perl Compatible Regular Expressions

Paul Welsh paul at welshfamily.com
Sat Dec 17 20:11:04 GMT 2011

Hi all

Apologies this is off topic.

I have a quick question about Perl Compatible Regular Expressions.
I'm using Exim 4.x and a greylist application in conjunction with
MailScanner obviously.

The greylist application has a whitelist to cope with senders that,
when greylisted, try sending again using a different server rather
than with the same one.

The whitelist is MTA dependent.  Exim supports Perl Compatible Regular
Expressions but I'm struggling to match on part of the hostname.  For
example, this works fine:
- matches mail.domain.com, xxx.mail.com, etc

What I want to match, however, is something like:
which would match say mail01.domain.com, mail02.domain.com, etc

I think I need to use the ^ symbol but after much googling can't
figure it out.  I've tried umpteen permutations to no avail.  Any

Alternatively, if what I'm seeking to do is very complex, does anyone
know whether Exim can cope with IP subnets that don't include a whole
octet?  I've discovered belatedly that the whitelist can cope with,
for example:
but not:

Any assistance gratefully received.

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