Techopedia explains
Electronic Mail (Email)
Email messages are relayed via email servers and provided by all Internet service providers.
Emails are transmitted between two dedicated server folders: sender and recipient. A sender saves, sends or forwards email messages, while a recipient reads or downloads them by accessing an email server.
Email messages are comprised of three components as follows:
- Message Envelope: Describes the email’s electronic format
- Message Header: Includes sender/recipient information and email subject line
- Message Body: Text, image and file attachments