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
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Expert Comment

Comment Utility
What language do you use to write the regular expression

Author Comment

Comment Utility
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,
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Expert Comment

by:Carl Bohman
Comment Utility
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

Comment Utility
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
Comment Utility
Found a regex that allowed me to limit the inbound/ outbound to only the two domains.

Author Closing Comment

Comment Utility
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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