[CentOS] Per-user limits for port access

Centos 5.x again...

Is there a way to limit port access on a per-user basis? My practical goal
is to limit, who is allowed to use SMTP AUTH in Sendmail. Any possible
solutions appreciated...

Obviously, limiting by ip will not work, since the very purpose of SMTP AUTH
is to enable mail relaying for trusted users from *anywhere*.

- Jussi

--
Jussi Hirvi * Green Spot
Topeliuksenkatu 15 C * 00250 Helsinki * Finland
Tel. & fax +358 9 493 981 * Mobile +358 40 771 2098 (only sms)
jussi.hirvi at greenspot.fi * http://www.greenspot.fi