a hard bounce is the failed delivery of an email due to a permanent reason like a non-existent address
A soft bounce is an email message that gets as far as the recipient’s mail server but is bounced back undelivered before it gets to the intended recipient. A soft bounce might occur because the recipient’s inbox is full.
the criminally fraudulent process of attempting to acquire sensitive information such as usernames, passwords and credit card details by masquerading as a trustworthy entity in an electronic communication
Encryption is the process of transforming information (referred to as plaintext) using an algorithm (called cipher) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key.
Decryption can typically also perform decryption), to make the encrypted information readable again