The BTMail emails are protected by network-level encryption. This layer of encryption protects your emails within the BTMail network or while they're in transit from sender to recipient.
If your Legal Company want a further level of encryption they will need to supply you with details of what encryption program they want you to use and what the encryption key is so that you can write it and then encrypt it before sending so that they can unlock it at their end in order to read it.
