Attacking Common Services - Easy - smtp-user-enum does not find any users

I have run smtp-user-enum against the target, using mode RCPT and the user list from the ressources section. I have also specified the domain “inlanefreight.htb”. The exact command which I have used is:

smtp-user-enum -M RCPT -U users.list -D inlanefreight.htb -t 10.129.47.123

However it does not find any users: