Decrypted mail blank in mail client

Hi Martijn,

Thank you very much for your super and super fast response!!

In fact, I did only learn about the opaque term from the Andreas Studenski mail you quoted.

Trying a quick fix, I did check Settings -> Edit Global preferences (advances) "Remove signature" unchecking "inherit". That will hopefully help with new mails but not with the hundreds of mails imported from Exchange suffering from the issue.

I will also post the issue to the Kopano forum. There, the term "opaque" was used eleven times, but in other contexts. I very much hope that I will be able to have Felix Bartels or others understand what we are talking about.



P.S: As both ciphermail and Kopano are Dutch, I shall say that being from Hamburg and living in Düsseldorf part time, I very much envy NL!


-----Ursprüngliche Nachricht-----

Von: Martijn Brinkers <martijn(a)>
Gesendet: Mittwoch 17 März 2021 18:09
An: users(a)
CC: Prof. Dr. Michael Schefczyk <michael(a)>
Betreff: Re: Decrypted mail blank in mail client

Hi Michael,

The most likely reason you cannot red the email is that the email was
first opaquely signed and then encrypted (probably by Outlook).

CipherMail removes the encryption but keeps the signed email. If the
email was opaquely signed (which is the default with Outlook when the
email is encrypted), you need an mail client which can handle opaquely
signed email. If you email client cannot handle opaquely signed email,
your best option for now is to have the gateway remove the signature
(see settings).

For a recent discussion about a similar issue see

I will spend some time investigating two options: is it possible to
convert an opaquely signed email to a clear signed email without
breaking the signature or, add an option to only remove the signature
if the email is opaquely signed

Kind regards,

Martijn Brinkers

CipherMail email encryption
Email encryption with support for S/MIME,
OpenPGP, PDF Messenger and Webmail Messenger

On Wed, 2021-03-17 at 17:01 +0000, Prof. Dr. Michael Schefczyk via > Users wrote:
> Dear All,
> For SOHO purposes, I have been using a chiphermail gateway for a long
> time, traditionally in front of an Exchange server. Recently, I did
> swich to Kopano - please feel free to guess why.
> There was one problem with decytped mails that annoyed me with
> Exchange but that is more critical with Kopano and I am unable to
> describe it adequately to Kopano. It might have to do with opaque
> signing or it might have other reasons.
> When I receive an SMIME-encrypted e-mail, the gateway does decrypt
> it. With Exchchange, the behavior was:
> - decrypted message was fully visible in outlook - one could work
> with it just as expected
> - on Android (LineageOS, standard mail client), the decrypted message
> was marked as encrypted and not presentable despite the fact that it
> was in fact decrypted.
> I found that annoying, but I could stand that. If needed, I did use
> OWA.
> With Kopano, the behavior is:
> - decrypted message is shown blank in Kopano client. When downloading
> in .eml format, it can be viewed (with Outlook, for example)
> - on Android, the decrypted message is also shown blank. Just an
> smime.p7m enclosure is visible.
> I would very much welcome, if Martijn or someone else could point me
> to the right direction to resolve this issue. Any help in describing
> the issue to Kopano and/or in understanding which features might have
> to be enabled in php and/or apache in use would be great.
> Thanks & Regards,
> Michael
> ____________________________________________________________
> Technische Universität Dresden
> Fakultät Wirtschaftswissenschaften
> Lehrstuhl für Entrepreneurship und Innovation
> Prof. Dr. Michael Schefczyk
> D-01062 Dresden
> Fon: +49-3 51-4 63-3 68 81
> Fax: +49-3 51-4 63-3 68 83