What service is being accessed?

Your server logfile shows repeated connections to TCP port 143. What service is being accessed?

A.
smtp

B.
imap

C.
pop3

D.
pop2

E.
nmbd

Explanation:
From /etc/services:
imap2           143/tcp         imap            # Interim Mail Access P 2 and 4
imap2           143/udp         imap