Installing and Administering Internet Services

Chapter 4 137
Installing and Administering sendmail
How sendmail Works
Figure 4-1 Flow of Mail Through sendmail
If an address resolves to the local mailer, sendmail looks up the address
in its alias database and expands it appropriately if it is found.
User
mailx mail elm
sendmail
Local Host
OpenMail
Delivery
Agent
X.400
Delivery
Agent
SMTP
Delivery
Agent
UUCP
Local
Mailer
User Agents
Delivery Agents
OpenMail
or X.25
Network
X.400
Network
Local
Area
Network
Telephone
Lines
Local
Mailboxes
Communications
Media
OpenMail
Receiving
Agent
X.400
Receiving
Agent
SMTP
Server
UUCP
Receiving Agents
sendmail
Destination Host
Local
Mailer
rmail
...
Mail
Recipient User
mailx mail elm
User Agents
rmail
...
Directory