There are two basic different approaches to developing an email application in Palm OS.
Our goal in this article is to accomodate incorporation of EMSD as a Mail Transport Service provider in both models.
In the separate mail user interface and mail transport service model, the application is split into two parts.
One part is responsible for transfering the mail message. The other responsible for processing and displaying the message.
An example of the first approach is the standard Mail application.
The basic distribution of Palm OS lacks mail trasnport services such as SMTP[79] or POP3[69]. It depends on its desktop synchronization to do the actual sending and receiving. Messages written by the user is put into a queue. Upon synchronising with the desktop, the desktop counterpart sends the queued messages and also put received messages into the queue.
However there are add-on packages, such as "Top Gun Postman"[37] that provides SMTP and POP3 supports within the Palm OS device for these softwares. This enables users of the standard Mail application to send and receive directly from their devices.
Incorporation of EMSD into packages such as ``Top Gun Postman'' can be quite rapidly accomplished as an add-on or replacement for SMTP/POP/IMAP.
Figure 16.1 illustrates the components involved as well as the layering of services in this model.
In the integrated mail user interface and mail transport service model, the application is self contained.
Examples of the this approach are numerous as they offer more convenience of operation and usage in the Palm OS environment. In particular:
"MsgAgent"[75] and "DoodleMail"[83] are very popular clients.
are two such examples.
Figure 16.2 illustrates the components involved as well as the layering of services.
