Communication and letter to post (1-4)
I believe the answer is:
I believe this clue is a triple definition!
'communication' is the first definition.
(I know that e-mail is a type of electronic communication)
'and' is a link.
'letter' is the second definition.
(I have seen 'Electronic letter ' mean 'e-mail' so perhaps 'letter' could also mean 'e-mail')
'to' acts as a link.
'post' is the third definition.
(I have seen 'Electronic post ' mean 'e-mail' so perhaps 'post' could also mean 'e-mail')
(Other definitions for e-mail that I've seen before include "Online correspondence" , "Electronic epistle" , "Web post" , "Electronic missive" , "Correspondence sent via internet" .)