Regular Expression Help

Posted on 2013-02-04
Last Modified: 2013-02-12

I need some help with the correct syntax of a regular expression for my spam filter. I have two domains let's call them domainA and domainB. The spam filter in question is part of domainB and is used to restrict inbound/ outbound email to only be allowed to DomainA. Since the spam filter support regular expression, it would be ideal to have a regular expression that says if not domainA or domainB then make as spam.

I have tried ^(domainA|domainB) and ^((?!domainA$)|(?!domainB$)).*$ without success.

Can somebody please help me with the correct syntax.

Thank you.
Question by:sysadmin-inq
  • 4

Expert Comment

ID: 38854013
What language do you use to write the regular expression

Author Comment

ID: 38854064
Usern_n, thanks for the reply the documentation for the spam filter does not say the language it just says the follow:

"A notification email is triggered when inbound or outbound message containing this value is encountered by the Rules Engine. Use regular expression to specify more than one address. For example:

In my case I want to only trigger the event / mark the email as spam if the address is not from domainA or domainB.

Thank you,
LVL 13

Expert Comment

by:Carl Bohman
ID: 38855335
Based on a quick web search, it looks like you might be using Barracuda.  If so, this is their documentation on regular expressions:

This appears to include only a small number of regular expression features.  Unfortunately, none of them include negation.  If there is an option to specify that a regular expression is a whitelist instead of a blacklist, use that.

While poking around a little on Barracuda's web site, I noticed that they recommend against whitelisting domains (due to spoofing).  More information, including additional ways to configure spam filters are here:
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Author Comment

ID: 38856083
Hi Bounsy,

I'm actually using software called Xeams, for the spam filter, not barracuda.  Do you know how to create the negative regex? I can test to see if negative regex works.


Accepted Solution

sysadmin-inq earned 0 total points
ID: 38864732
Found a regex that allowed me to limit the inbound/ outbound to only the two domains.

Author Closing Comment

ID: 38879457
The regex does what I'm looking for to limit mailflow to only the two domains and marks all other domains a spam via the spam filter.

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