406 Interactive Mail Support Protocol - System Port

406 is a System Port. Transport Protocol TCP UDP , 406 Service Name imsp, Service Name Description: Interactive Mail Support Protocol.

Port	Protocol	Service Name	Description	Source
406	TCP UDP	imsp	Interactive Mail Support Protocol	IANA
406	TCP UDP	imsp	Interactive Mail Support Protocol	bekkoame

Port	Service Name	Description
474	tn-tl-w1	tn-tl-w1
1239	nmsd	NMSD
2511	metastorm	Metastorm
2740	alarm	Alarm
3195	ncu-1	Network Control Unit
7190		Unassigned
7228	citrixupp	Citrix Universal Printing Port
8146		Unassigned
8349		Unassigned
8460		Unassigned

A port is an endpoint of communication in an operating system. While the term is also used for hardware devices, in software it is a logical construct that identifies a specific process or a type of service.

Port numbers are assigned in various ways, based on three ranges: System Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private Ports (49152-65535);

The Well Known Ports are assigned by the IANA and on most systems can only be used by system (or root) processes or by programs executed by privileged users. Ports are used in the TCP [RFC793] to name the ends of logical connections which carry long term conversations. For the purpose of providing services to unknown callers, a service contact port is defined. This list specifies the port used by the server process as its contact port. The contact port is sometimes called the "well-known port". To the extent possible, these same port assignments are used with the UDP [RFC768]. The range for well-known ports managed by the IANA is 0-1023.
DYNAMIC AND/OR PRIVATE PORTS Registered Ports are those from 1024 through 49151.
The Dynamic and/or Private Ports are those from 49152 through 65535