When trying to sign messages with thunderbir on debian mails won't deliver. If they are not signed, it will send smoothly even if they are encrypted. :~$ lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux trixie/sid Release: n/a Codename: trixie :~$ dpkg -l |grep thunderbird ii thunderbird 1:115.7.0-1 amd64 mail/news client with RSS, chat and integrated spam filter support :~$ dpkg -l |grep gnupg ii gnupg 2.2.40-1.1 all GNU privacy guard - a free PGP replacement ii gnupg-l10n 2.2.40-1.1 all GNU privacy guard - localization files ii gnupg-utils 2.2.40-1.1+b1 amd64 GNU privacy guard - utility programs using gnome-desktop-3 :~$ dpkg -l |grep pinentry ii pinentry-curses 1.2.1-3 amd64 curses-based PIN or pass-phrase entry dialog for GnuPG ii pinentry-gnome3 1.2.1-3 amd64 GNOME 3 PIN or pass-phrase entry dialog for GnuPG