In order to provide for the exchange of email on different computers, using different email programs, it was necessary to define standard formats for the transmission and exchange of email.
The computer industry developed two main approaches:
- Internet-based standards
By about 1994, the internet-based approach became dominant. This was mainly due to the:
- Spread of the internet
- Simplicity of using internet rather than X.400 email addresses
- Cheapness of internet mail. With X.400, service providers would charge for email transmission; with internet mail, once you had an internet connection in place, it was free.