If the recipient already has a REDDCRYPT account they can read the email immediately after opening their app.
If this is their first time receiving an encrypted REDDCRYPT email they will be prompted to enter the defined passphrase after clicking on the mail.
In order to securely communicate the passphrase we recommend a media disruption, i.e. communicating the passphrase via SMS, phone call or letter to the recipient. In any case, the passphrase should not be communicated via email.