PGP/MIME encrypted messages injected into a Vaultive O365 (before 4.5.21) frontend via IMAP or SMTP have their Content-Type changed from 'Content-Type: multipart/encrypted; protocol="application/pgp-encrypted"; boundary="abc123abc123"' to 'Content-Type: text/plain' - this results in the encrypted message being structured in such a way that most PGP/MIME-capable mail user agents are unable to decrypt it cleanly. The outcome is that encrypted mail passing through this device does not work (Denial of Service), and a common real-world consequence is a request to resend the mail in the clear (Information Disclosure).