[ale] message header to identify "read" email

[Jim Popovitch]

I need some general input/advice.  I am using something (think:
procmail) to tag some emails prior to reading them in Evolution.  What I
want to do is add a header to the message (easy enough) and then a
filter in Evolution to recognize the header and set the message as
already read (again, easy enough).  NOTE: This will be something
distributed to others.

What I need input on is the name of the message header field.  I thought
of using something like "X-MessageRead = Yes", but was wondering if
there is a standard header that might be used elsewhere for the same
purpose.  Ideally it would be nice if there was a known header that
email applications would automatically recognize and use.

Any and all feedback is appreciated.

Thx,

-Jim P.