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).
The product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required.