dovecot/templates/default/conf.d/auth-deny.conf.ext.erb

# Deny access for users. Included from auth.conf.

# Users can be (temporarily) disabled by adding a passdb with deny=yes.
# If the user is found from that database, authentication will fail.
# The deny passdb should always be specified before others, so it gets
# checked first.

# Example deny passdb using passwd-file. You can use any passdb though.
passdb {
  driver = passwd-file
  deny = yes

  # File contains a list of usernames, one per line
  args = /etc/dovecot/deny-users
}