Today I will share my experience on configuring regular expression for automatic or recommended classification. The configuration in Azure Portal is quite straight forward. If you wish to know how to configure, Microsoft actually documented well. Refer to https://docs.microsoft.com/en-us/information-protection/deploy-use/configure-policy-classification
This is how the configuration looks like:
Okay, back to the custom condition, it supports Word, Phrase, and Regular Expression. Talking about Regular Expression, there is a lot regular expression tester out there. I personally like this one, http://regexr.com/.
Taking (#[A-Z][A-Z&][A-Z][0-9][0-9][0-9]#) as example, after I built the regular expression, I can test it out at the bottom, and it will be highlighted in blue if it match the regular expression. It is so easy and convenient. After you satisfied, copy the regular expression and paste it to the Azure Portal. Enjoy!!