This is one of the basic concepts and you may be asked about this in your interview.
An email consists of three important components:
- Envelope: Internal process by which the email is enrooted
- Email Header
- Main Body: Text Contents
Email header or header is nothing but the first part of any email message. The header contains information like the subject of the email, who is the sender, the date, which are compulsory. The optional headers are Subject and CC which are very commonly used. When the email is forwarded the date, time, subject become one of the headers with the body of the email.