forwarding a signed email

Ingo Klöcker kloecker at
Sat Nov 27 13:00:37 CET 2010

On Saturday 27 November 2010, Mike Korizek wrote:
> On 11/26/2010 08:46 AM, Olav Seyfarth wrote:
> >> Is it possible to forward a digitally signed email without loosing
> >> the signature information of the email?
> > 
> > Yes, inline/cleartext signed messages may just be forwarded as they
> > are (as attachment or as copy, just don't quote them ;-) ).
> > PGP/MIME signed messages should be forwarded as attachment in
> > order not to lose the sig.
> Hi Olav
> I did some tests with different email clients by forwarding it as
> attachment.
> Unfortunately the clients add different content-disp, -type.
> E.g. Evolution makes a content-disp inline whereas Thunderbird makes
> a content-type rfc822.

The value of Content-Disposition is irrelevant and shouldn't cause any 
problems. The correct Content-Type for attached messages is 

FWIW, KMail sets Content-Type message/rfc822 and Content-Disposition 
inline when forwarding messages as attachment.

> I need to pares the email with perl in order to extract the original
> email so I can verify the signature -

KMail can verify signatures of forwarded signed messages out-of-the-box. 
It nicely displays a signed forwarded message (including the signature 
status) inline in the enclosing signed message. In fact, this works for 
arbitrary deeply nested signed and/or encrypted messages. Think 
Matryoshka doll. :-)

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