Hi,
The token (?i) that indicates the rest of the regular expression should be treated in case-insensitive mode. Placing this token at the beginning of a case-sensitive regular expression results in a completely insensitive match.
For example, the regular expression “(?i)example” matches Example, eXAmplE, and EXAMPLE.
Please check table "Regular Expression in Rules" of the user guide, as it contains the various regex used in ESA and their descriptions.
You can download the user guides from this link:
http://www.cisco.com/c/en/us/support/security/email-security-appliance/products-user-guide-list.html
Cheers,
Zaid Al-Ali
