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You don't need the parentheses unless you are replacing the value.<br />
Here is the simplest regex. <br />

<pre><code id="code-8268984">[3-9]\d\d</code></pre>
<br />
You can test it here.<br />
<a href="http://regexr.com/3asi6" rel="ugc">http://regexr.com/3asi6</a>
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The [] and - syntax isn't shown as supported for the Transport Rules Regex. &nbsp;See the Exchange link. &nbsp;The regex I have works on test sites, it just doesn't work 100% of the time on Exchange.
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^(3\d\d|4\d\d|5\d\d|6\d\d|<wbr />7\d\d|8\d\<wbr />d|9\d\d)$ works better. &nbsp;It missed a single 945 over several days.<br />
<br />
It's not a fix for what seems to be an Exchange bug, but a reasonable workaround.<br />
<br />
Thanks.
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I'm trying to match a numeric header value to between 300 and 999.<br />
<br />
The condition is &quot;when the message header matches text patterns&quot;<br />
<br />
I'm using ^(3|4|5|6|7|8|9)\d\d$ based on <a href="https://technet.microsoft.com/en-us/library/aa997187%28v=exchg.141%29.aspx" rel="ugc">https://technet.microsoft.com/en-us/library/aa997187%28v=exchg.141%29.aspx</a><br />
<br />
It's working for 300-999, but it's also matching values like 85 and 215. &nbsp;It seems to match any value with at least 2 digits.<br />
<br />
Is my regex correct? &nbsp;Does regex work correctly for header values?
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I'm trying to match a numeric header value to between 300 and 999.

The condition is "when the message header matches text patterns"

I'm using ^(3|4|5|6|7|8|9)\d\d$ based on https://technet.microsoft.com/en-us/library/aa997187%28v=exchg.141%29.aspx

It's working for 300-999, but it's also matching values like 85 and 215.  It seems to match any value with at least 2 digits.

Is my regex correct?  Does regex work correctly for header values?

You don&#39;t need the parentheses unless you are replacing the value.
Here is the simplest regex. 


You can test it here.
http://regexr.com/3asi6

The [] and - syntax isn&#39;t shown as supported for the Transport Rules Regex.  See the Exchange link.  The regex I have works on test sites, it just doesn&#39;t work 100% of the time on Exchange.

^(3\d\d|4\d\d|5\d\d|6\d\d|7\d\d|8\d\d|9\d\d)$ works better.  It missed a single 945 over several days.

It&#39;s not a fix for what seems to be an Exchange bug, but a reasonable workaround.

Thanks.

Exchange 2010 Transport Rule Regex not working as expected

I&#39;m trying to match a numeric header value to between 300 and 999.

The condition is &quot;when the message header matches text patterns&quot;

I&#39;m using ^(3|4|5|6|7|8|9)\d\d$ based on https://technet.microsoft.com/en-us/library/aa997187%28v=exchg.141%29.aspx

It&#39;s working for 300-999, but it&#39;s also matching values like 85 and 215.  It seems to match any value with at least 2 digits.

Is my regex correct?  Does regex work correctly for header values?

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

A regular expression ("regex") is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. Regular expression processors are found in several search engines, search and replace dialogs of several word processors and text editors, and in the command lines of text processing utilities, such as sed and AWK. Many programming languages provide regular expression capabilities, some built-in, for example Perl, JavaScript, Ruby, AWK, and Tcl, and others via a standard library, for example .NET languages, Java, Python and C++ (since C++11). Most other languages offer regular expressions via a library.