sorter vs mailsorter

sorter and mailsorter both are nouns.

Word	Noun	Adjective	Verb	Adverb
sorter	Yes	No	No	No
mailsorter	Yes	No	No	No

As nouns, mailsorter is a hyponym of sorter; that is, mailsorter is a word with a more specific, narrower meaning than sorter:

sorter: a machine for sorting things (such as punched cards or letters) into classes
mailsorter: a sorter for sorting mail according to the address

Other hyponyms of sorter include collator.

sorter (noun)	mailsorter (noun)
a machine for sorting things (such as punched cards or letters) into classes	a sorter for sorting mail according to the address
a clerk who sorts things (as letters at the post office)