Quick Answer is NO.

I would suggest using the Subject  for this with all Caps.

The Long Answer.

This is a none standard protocol that you probably remember from Outlook. In actuality it never worked well and most the time would either get removed from the email during the process and or not supported by the end user.

See Help Links Below.

http://www.google.com/support/forum/p/gmail/thread?tid=127e7b6566c71fd7&hl=en

http://www.google.com/support/forum/p/gmail/thread?tid=7881c84c1ae9d7ee&hl=en

Quick Answer is NO.

I would suggest using the Subject  for this with all Caps.

The Long Answer.

This is a none standard protocol that you probably remember from Outlook. In actuality it never worked well and most the time would either get removed from the email during the process and or not supported by the end user.

See Help Links Below.