Sha mail

You're referring to SHA (Secure Hash Algorithm) mail!

SHA is a cryptographic hash function that produces a fixed-size string of characters (a "digest") from a variable-size input message. It's commonly used to verify the integrity and authenticity of data, such as emails.

In the context of email, SHA is often used to create a digital signature or a message digest. Here's how it works:

1. The sender generates a SHA-256 (or another SHA variant) hash of the email message, including the headers, body, and any attachments.
2. The sender encrypts the hash using their private key to create a digital signature.
3. The sender attaches the digital signature to the email.
4. The recipient verifies the digital signature by decrypting it with the sender's public key and comparing the resulting hash with the SHA-256 hash of the received email message.

If the two hashes match, the recipient can be confident that the email has not been tampered with or altered during transmission. This ensures the integrity and authenticity of the email.

SHA is widely used in email protocols, such as S/MIME (Secure/Multipurpose Internet Mail Extensions) and PGP (Pretty Good Privacy). It's an essential tool for securing email communications and protecting against email spoofing, tampering, and other forms of cyber attacks.