dovecot - Dec 2009 - force PLAIN auth mech?

I have

auth_default {
  mechanisms = plain
}

yet clients are able to login using cram-md5.  how can i force use of plain?

On December 17, 2009 12:45:16 PM -0500 Frank Cusack <fcusack at
fcusack.com>
wrote:
> I have
>
> auth_default {
>   mechanisms = plain
> }
>
> yet clients are able to login using cram-md5.  how can i force use of
> plain?
the reason i think folks are using non-plain is that i see resp=... in
the auth debug, as opposed to pass=... .