Qmail is taking ages to authenticate outgoing mail. In fact folks trying to send with Outlook find it times out (Eudora is slow, but OK).

Ping or trace route to the mail server is fine. The server itself is not at all loaded. Picking up incoming mail is fast. It's just trying to send that is so slow. This is global across the server (not just one or two domains).

Is there some setting I need to tweak?

check your DNS configuration on the box at /etc/resolv.conf

try disabling DNS lookups in your qmail and syslog logs

regards

Thanks - I'll take a look at that