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
1105	ftranhc	FTRANHC
1286	netuitive	netuitive
1559	web2host	web2host
1733	siipat	SIMS - SIIPAT Protocol for Alarm Transmission
1800	ansys-lm	ANSYS-License manager
3245	vieo-fe	VIEO Fabric Executive
3382	fujitsu-neat	Fujitsu Network Enhanced Antitheft function
3620	ep-pcp	EPSON Projector Control Port
4587		Unassigned
4907		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