Enter the flag:
Claim Command:
/challenge claim challenge:enumeration-6 flag:<answer>
Find a weird user on the SMTP server.
They're not one of these:
bin
daemon
ftp
games
guest
halt
lp
mail
man
news
nobody
ntp
operator
postmaster
postfix
root
ROOT
shutdown
sshd
sync
uucp
www
(hint: /usr/share/wordlists/metasploit/unix_users.txt is a good wordlist)
Box: luhack-enum-0