[CipherMail User] What Cert is used (domain vs. user)?

Hi, is there a setting to see information about the cert that is actually used to encrypt to a message? Background: Domain example.com uses user specific certs. If a user sends a signed mail, ciphermail stores the cert as expected. Sending S/MIME encrypted mails to a user at example.com depends if there is a the stored cert. Now we like to set up domain-domain-encryption. example.com send a cert for the domain. I created a domain in ciphermail and enabled the domain cert they send. Now mails to every user at example.com can be send encrypted - with the domain cert. Users at example.com complain that they cannot decrypt the mail. Is there any precedence of user cert to domain cert in ciphermail? Information what cert ciphermail actually used to encrypt the message is needed. Regards, Marc