12. The method as claimed in claim 9 , further comprising: receiving a header name to be searched; converting the header name to its canonical key using the mapping; and searching for the canonical key in the message header list of a message using integer comparison.
9. The method as claimed in claim 1 , further comprising: receiving a message having a message header of header names; converting the header names to canonical keys; and building a message header list for the message of the canonical keys.