Slightly odd problem has arisen during boot-up. It was working fine, but now when it goes through all the messages at startup, when it reaches the two about "Sendmail" it stops and spends a very long time on them.

Once it's finished it boots up just fine, and according to Nmap the mail port is open & running.

But I haven't done anything to Sendmail yet. The only things I changed yesterday were:

Setting it to turn off the computer after shutdown
Setting up pilot-link (and USB as well as part of this)
Changing /etc/HOSTNAME and /etc/hosts to stop the computer calling itself "darkstar"

My current guess is that maybe I mis-configured the host file so Sendmail is spending a long time trying to find localhost - but I'd have thought it would either succeed straight away, or give and error message and give up. Instead, it works just fine, after spending several minutes starting up.

Any suggestions?

i had this same problem some days ago.i seems to be because sendmail
have problem with changed host name.look at boot log files to know what happened.
since i didnt use it i just disabled it by opening system services and unchecking it.(redhat-config-services)

Right. So looks like it IS the host name then. Cheers, I'll see what I can find..

The problem is in the file /etc/hosts.
Check for that:
127.0.0.1 machine.domain.example machine

You must have an address attach with the name of
the computer.

The delay is cause by the resolver, sendmail try to
check what is the address of the domain. If is not able
to find it, it must try many times and after that
giving up.

Richard