Problems with sendmail

[Jonathan]

Hi all,

I've just upgraded a server from 4.3-RELEASE to 4.8-STABLE and I'm now 
having sendmail problems. I was intending to leave the original sendmail 
in place, pending a migration to qmail, but unfortunately, I made use of 
the wrong make.conf and I'm now sitting in front of a new sendmail setup 
and I've not used sendmail for about 7 years.

The original problem was permission denied on /var/spool/clientmqueue 
which I sorted by chowning to smmsp:smmsp.

I'm not getting the following in the logs (when trying to send email 
through PHP's mail function):

Jun 12 08:13:51 server3 sendmail[59396]: h5C7DphJ059396: from=www, 
size=81, class=0, nrcpts=0, 
msgid=<200306120713.h5C7DphJ059396 at server3.sirtis.co.uk>, 
relay=www at localhost
Jun 12 08:13:51 server3 sendmail[59396]: h5C7DphJ059396: h5C7DphK059396: 
DSN: testing at sirtis.co.uk; jonathan at sirtis.org.uk... Invalid route address

I'm sure this is a simple problem, but I'm not sure where to start. Any 
assistance would be much appreciated.

My main fear is screwing the server up - it's running correctly for 
incoming mails for the domains configured on it and emails from the 
command line are working, so I'm assuming that I need to setup 
authorisation for sirtis.co.uk to send mail?

TIA,

Jonathan