This report is probably related to 2614 and 2778. However, the information provided in these bug reports do not resolve my problem. I use Claws Mail on Linux Mint Debian Edition. I use Kleopatra for key managment. === The Problem === I have two X.509 certificates issued on my name and email address in my keyring. These are issues by different CAs and I need both of them, so I cannot remove one or simply use the newest, as suggested in the mentioned bug reports (2614 and 2778). When I compose an email and try to sign it with s/mime Claws Mail says: "Secret key specification is ambiguous". The actual Message in my localization is "Fehler bei digitaler Signatur: Angaben zum privaten Schlüssel sind mehrdeutig.", if this is of any interest. === What should happen === I suppose Claws Mail should ask which key to use for signing or give the user another way to choose the right key.