Not escaping "from"

Occasionally an automated anti-spam message will bounce.  When it does,
procmail gets it as one message, but the OpenWindows mailtool sees it as
two or three.  The reason is that neither the outgoing nor the incoming
message have the  >  added to the embedded "From" lines.

Could the reason for this have anything to do with the following recipe?

# Regenerate "From" lines to make sure they are valid
:0 fhw
| formail -I "From " -a "From "

What actually does this recipe do?  (I didn't write it)