Problem with PGP-signed E-Mails

[hede]

Am 2018-06-14 08:42, schrieb T. Mohrfeldt (Liesegang GmbH):

> Mail in Sent-Folder Signature intact:
> [...]
>> Content-Transfer-Encoding: 8bit
>> Content-Type: text/plain; charset=UTF-8
>> 

vs.

> Mail on the recipient's side, signature invalid:
> [...]
>> Content-Type: text/plain; charset=UTF-8
>> Content-Transfer-Encoding: quoted-printable
>> 

Something changed the encoding, rendering the signature invalid.

Wallace!?