[Mailman-Users] tweaking mails

[bergenpeak at comcast.net]

On some of the mailman lists I manage, there might be some value if when 
the mail comes in to mailman, if I could parse the mail looking for key 
phrases or terms and based on what is found, either tweak the mail 
contents and/or insert some additional information above or below the 
mail's contents before mailman sends this updated mail message out to 
the subscribers.

The information added to the mail could be based on the mail's contents 
and/or information maintained in a file that would be tracking the info 
that was added in previous mails.

Is this possible?  Issues to be aware of in doing this?

Thanks