Relationship of EMSD to Other Mail Protocols

EMSD is designed to be a companion to existing Internet mail protocols. It is designed to fit within the many protocols already in use for messaging, as well as those already in use for networking.

Figure 4 shows how EMSD fits in with the other major messaging protocols. The RFCs referenced in the figure are current at the time of this writing, but could be updated or made obsolete at any time.

Figure 4: Messaging Communication Stack and EMSD

The various Internet mail protocols provide different sets of capabilities for mail processing. Table 2 summarizes the capabilities of SMTP, IMAP, POP and EMSD in the following areas of functionality:

• Mail Submission
• Mail Delivery
• Mail Routing (Relay)
• Mail Retrieval
• Mailbox Access
• Mailbox Synchronization

Table 2: Messaging Protocol Functionality

Protocol Function	SMTP	IMAP	POP	EMSD
Submission	XX			XXX
Delivery	XXX			XXX
Relay (Routing)	XXX
Retrieval		XXX	XXX	XX
Mailbox Access		XXX	X
Mailbox Sync.		XXX

The number of X's in each cell of the table denotes the extent to which a particular function is supported by a particular protocol.

Table 2 clearly demonstrates that combinations of these protocols can be used to complement one other in providing rich functionality to the user. For example, a user interested in highly mobile messaging functionality can use EMSD for the submission and delivery of time-critical and important messages, and use IMAP for comprehensive access to his/her mail-box.