class Net::IMAP

def setacl(mailbox, user, rights)

[RFC4314[https://tools.ietf.org/html/rfc4314]].
The server's capabilities must include +ACL+

===== Capabilities

Related: #getacl

rights to that mailbox.
mailbox. If +rights+ is nil, then that user will be stripped of any
along with +mailbox+, +user+ and the +rights+ that user is to have on that
Sends a {SETACL command [RFC4314 ยง3.1]}[https://www.rfc-editor.org/rfc/rfc4314#section-3.1] 
def setacl(mailbox, user, rights)
  if rights.nil?
    send_command("SETACL", mailbox, user, "")
  else
    send_command("SETACL", mailbox, user, rights)
  end
end