What is the meaning of the word "post"?

Definitions:

a job in an organization noun
- The new hire occupied a post in the treasury.
a pole or stake set up to mark something (as the start or end of a race track) noun
- a pair of posts marked the goal
affix in a public place or for public notice verb
- post a warning
an upright consisting of a piece of timber or metal fixed firmly in an upright position noun
- The posts in the ground with strung barbwire made for a cattle fence.
assign to a post verb
- put into a post
military installation at which a body of troops is stationed noun
- this military post provides an important source of income for the town nearby
place so as to be noticed verb
- post a sign
publicize with, or as if with, a poster verb
- I'll post the news on the bulletin board
the delivery and collection of letters and packages noun
- it came by the first post
the position where someone (as a guard or sentry) stands or is assigned to stand noun
- a soldier manned the entrance post