[imp] How to get envelope-sender header

[Camilo Echeverry]

Hi.
I was triying to search about this issue in google and figured out
that all messages have the "envelope-sender" words so I couldn't find
anything.

My question is:
Is there some imp/horde/php/imap  function to retrieve the
envelope-sender header from a mail.
This is because I want to incorporate some external filters which need
this value.
Thanks a lot.

Camilo.

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