I have some questions about the "Last-Mile encryption" and "Encrypted Voicemail". Does Cape receive cleartext and resend it encrypted? What does this achieve? Integrity? Does the service drop unencrypted messages?

We receive in cleartext and encrypt with a key controlled by the customer. Most carriers store voicemail and SMS in cleartext on their servers. The goal is reduce exposure while preserving interoperability. This post on encrypted voicemail gets into more technical details about how it works: https://www.cape.co/blog/product-feature-encrypted-voicemail...