Hello,
There are two ways of encryption of Emails that can be handled via BC / SMTP:
1. Office 365 SMTP / UseSSL
2. third party SMTP over port 465 (via third party SMTP mail server); in older versions of .NET this explicit SMTPs was not yet supported (maybe that changed in later .NET releases).
Apart from that we do have data encryption that can be enabled and SQL Server encryption.
Thanks.