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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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An additional example<br />

In the following scenario, user abc at host vm1.stockholm.ibm.com sends a note<br />

to users xyz, opq, <strong>and</strong> rst at host delta.aus.edu (Figure 15-3). The lines preceded<br />

by R: are lines sent by the receiver; the S: lines are sent by the sender.<br />

Figure 15-3 SMTP an example scenario<br />

Note that the message header is part of the data being transmitted.<br />

15.1.2 SMTP <strong>and</strong> the Domain Name System<br />

If the network is using the domain concept, an SMTP entity cannot simply deliver<br />

mail sent to TEST.MYCORP.COM by opening a <strong>TCP</strong> connection to<br />

Chapter 15. Mail applications 565

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