what are the possible sendmail syslog delivery states?

in /var/log/mail sendmail writes what has been done with the mail
e.g. date host sendmail[pid]: sendmailid: to= XXXX@XXXXX.COM , ctladdr=usr 
(0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30288, 
relay=[host] [host], dsn=version, stat=Sent (sendmailid Message accepted 
for delivery)

i checked the sendmail source code, but i cant find any hint for a list 
of possible sendmail delivery states?

for now i know they can be:
stat=Sent (text from recipient mail server)
stat=queued
stat=Deferred: reason
stat=User unkown

and what does every state mean?
Sent = ok, sent
queued = its in the queue
deferred = ? (i think sendmail tried to send, but maybe remote host is 
down so it couldnt deliver the mail -> deferred??)
user unkown = recipient mail address not found, so no delivery

which other states are available? and where the hack are the states 
defined? i really found nothing in sendmail source, which could help

thx