The cost models for Internet mail and X.400 have traditionally been
rather different: An X.400 service provider will charge the sender for
each message sent according to some tariff, while an Internet service
provider charges you for "bandwidth to the Internet".
A special class of mail user is the dialup or occasionally connected Internet user; in this case, the service provider will commonly provide a "mail spool" and charge for connect time; in effect the recipient is paying for reading mail.
The recipient of Internet mail also bears all the costs of making sure the messages can reach him, by arranging for DNS records, secondary mail servers and other infrastructure.
For an X.400 service, the idea is that the sender pays for the message, the recipient pays for the connectivity.
Typical numbers for the two kinds of connectivity:
Internet, some example prices from Norway:
Note also that with an Internet connection, you get access to all Internet services; with an X.400 connection, you get access to X.400 service; the marginal cost of doing E-mail over the Internet may be small if you paid for the line out of a budget dedicated to Web-browsing, for instance.
Further confusing the issue, some X.400 service providers offer access to their X.400 service through the Internet.Harald.T.Alvestrand@uninett.no Last modified: Mon Aug 26 15:17:12 1996