Completely remove user from system

[itpr0]

Hi list,

We are using postfix with system user authentication, I have to completely
remove an user for the system so he couldn't auth to send e-mails.

Some coworkers told to just remove the lines from /etc/passwd and
/etc/master.passwd... I did that but the user still can authenticate.

using "pw user show XXX" returns that still have a register from the user
XXX but trying the "pw user del XXX" it says there is no such user..

I tried rmuser and here is the return:

# rmuser XXX
Matching password entry:

XXX:*:20887:1014::0:0:XXXXX XXXXX:/home/XXX:/nonexistent

Is this the entry you wish to remove? y
Remove user's home directory (/home/XXXX)? y
Removing user (XXX): home passwdpw: user 'XXX' does not exist: No such file
or directory

There is any other thing that I can do to completely remove this user? It's
urgent 'cos it's sending a lot of spam mails :( and our server administrator
is on vacation :/
Thank you.