X.400 mail is more expensive to use than Internet Mail

• What you pay for your own infrastructure to carry the message
• What you pay for the service where you get the message transferred.

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:

X.400:

• P1 connectivity for a PRMD of 50 users: NOK 31.200 a year (USD 4800)
• Per message cost, beyond 2000 messages/month: NOK 1 per message (USD 0.15)

Internet, some example prices from Norway:

• Dialup access: NOK 2268 per year (USD 350), unlimited usage (EUNet Norway)
• Leased line, 64 Kbps: NOK 45.600 per year (USD 7000), unlimited usage (Interlink, Norway)

• Dialup access: USD 360/year, 25 hours/month (UUNet)
• Leased line, 56 Kbps: USD 8340/year (UUNet)
• Frame relay, 56 Kbps: USD 6540/year (UUNet)

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.