Subject Enryption trigger


i have a question regarding the subject enryption trigger.

Can the logic behind it reversed?

Want i want to archive is:

Every outgoing mail must be encrypted, if the mail can't be encrypted, the
template should be send back to the user.

The user can then use a subject trigger or something like that, so that this
mail will be send unencrypted to the recipient.

Kindly regards,

Ralf Kirmis