| Address model | Open and guessable — once known, it can be used indefinitely | Opaque handle; a Reach Contract is required before delivery |
| Revoking a sender | Usually means changing your number or address | Revoke that one contract — everything else keeps working |
| Purpose separation | One inbox for support, marketing, personal, and spam | Transactional, support, social, and marketing stay distinct |
| Lost device | The number or account itself is exposed | Revoke the device; your identity and other devices are unaffected |
| What the server sees | Varies by provider — often full message content | Encrypted envelopes and delivery metadata. On Android and desktop, never plaintext — the hosted web app differs |