SIP
493 Undecipherable
The request body was encrypted with S/MIME but the server cannot decrypt it. The server may lack the necessary key or certificate.
When You See This Code
When using S/MIME encryption for SIP message bodies and the recipient does not have the corresponding decryption key.
How to Fix
Ensure the recipient has the correct S/MIME certificate and private key. Consider using TLS for transport-layer encryption instead.