Service Name,Usage,Reference
rcmd,remote command/rlogin/telnet,
host,generic host-based service,[RFC2743]
imap,mailstore access/IMAP4,[RFC3501][RFC9051]
pop,maildrop access/POP3,[RFC5034]
acap,remote configuration access/ACAP,[RFC2244]
nfs,distributed file system protocol,[RFC2623][RFC7530][RFC8881]
ftp,file transfer/FTP/TFTP,[RFC2228]
ldap,Lightweight Directory Access Protocol (LDAP),[RFC4510][RFC4513]
smtp,message transfer/SMTP,[RFC4954]
beep,Blocks Extensible Exchange Protocol,[RFC3080]
mupdate,Mailbox Update (MUPDATE) Protocol,[RFC3656]
sacred,Secure Available Credentials (SACRED) Protocol,[RFC3767]
sieve,ManageSieve Protocol,[RFC5804]
xmpp,Extensible Messaging and Presence Protocol (XMPP),[RFC6120]
nntp,Network News Transfer Protocol (NNTP),[RFC4643]