| Test Objective Covered: 3. Describe how NetMail works. Before we get into the installation and configuration of NetMail, the CLE objectives specify that you be able to describe the way NetMail processes messages. Let's look at a general overview of the process that occurs when the NetMail server receives a message. This process applies to both incoming and outgoing messages. When NetMail receives a message, two files are created in the Message Queue: a control file and a data file . The control file contains sender and recipient addresses, priority flags, and message-processing information. The control file is named C nnnnnnn . in where nnnnnnn is a hashed version of the date and time when the file was received. The data file contains the message itself. The file is named D nnnnnnn . in where nnnnnnn is a hashed version of the date and time when the file was received. After the message has been completely received and saved in the Message Queue, the data file is renamed with an .msg extension. The control file passes through nine stages. In each stage, specific operations are performed on it. Tip Be aware that Novell refers to each of these stages as a queue . This terminology is somewhat misleading. It makes it sound like there are nine different directories that the control file passes through. This is not the case. Instead of queue , this book will refer to these as stages to clarify exactly what is happening to the control file.
After a given operation has been performed, the extension of the control file is changed, indicating that the file is ready for the next stage. Be aware that, although the extension changes, the hashed part of the control filename remains the same. The following processes occur: -
Stage 0 ” The extension of the control file is changed from .in to .000 . In this stage, the NMAP Agent verifies that the control file is valid. Then it directs the AntiVirus Agent (if configured) to scan the data file associated with the control file. If the message has attachments, they are delivered to the third-party virus scanning engine you configured the AntiVirus Agent to use. If found clean, the message progresses to Stage 1. -
Stage 1 ” The control file is given an extension of .001 . In this stage, the NMAP Agent directs the AntiSpam Agent to check the control file and ensure the message meets the antispam rules you have configured. If it does, the NMAP Agent directs the List Agent to check the control file to see if the message is intended for the NetMail List server. If so, the List Agent creates a new message from the original message for each recipient in the list. Each of these new messages is returned to Stage 0 and processed individually. The List Agent then deletes the original message. -
Stage 2 ” The control file is given an extension of .002 . In this stage, the NMAP Agent directs the Alias and the AutoReply Agents to process the control file. If the Alias Agent matches a recipient to a user object's alias, the Alias Agent replaces the alias with the correct email address. The AutoReply Agent checks the recipient's autoreply and forwarding rules and then takes action accordingly . -
Stage 3 ” The control file is given an extension of .003 . In this stage, the NMAP Agent checks for any rules defined in the recipient's user object (shown in Figure 10.24) and applies them. Figure 10.24. User message rules. 
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Stage 4 ” The control file is given an extension of .004 . This stage is not currently used by a NetMail agent. -
Stage 5 ” The control file is given an extension of .005 . In this stage, the control file is processed by the Calendar Agent to see if the message is an appointment or a response to an appointment (such as an Accept or Decline message). If so, the Calendar Agent processes the message using the parameters it has been configured to use and updates the recipient's MAIN.cal file. -
Stage 6 ” The control file is given an extension of .006 . In this stage, the NMAP Agent processes the control file to see if the message is intended for internal NetMail users. If so, the message is delivered to the intended recipients. -
Stage 7 ” The control file is given an extension of .007 . This stage is only applied to outgoing messages. If this stage is reached, the NMAP Agent processes the control file and delivers the message to the SMTP Agent. The SMTP Agent then sends the file to the destination email server. -
Stage 8 ” The control file is given an extension of .008 . This stage is hit only when a message is returned as undeliverable. The bounced message is kept in this stage until the system is idle. Then the control and data files are reprocessed, starting at Stage 0, in an attempt to redeliver the message. In each of these stages, if a NetMail agent modifies the original message, its extension is changed back to .000 and it is returned to Stage 0 for reprocessing. With this process in mind, let's now spend some time covering how to install and configure NetMail. |
