[CentOS] Lightweight MTA for XEN CentOS guests

All,

For a production environment, I'd like to setup CentOS XEN guests as
lightweight as possible.  I'd like the XEN guests to be able to send
nightly email as all CentOS servers do, but there is no reason to run
a mail server as the CentOS Dom0 already has an email server running
that can act as an email smart host.

The options that seem most appealing to me are either ssmtp or
sendmail minimally configured to only run the queuing submission
agent.

As far as ssmtp, I have not as yet found an CentOS RPM, presumably a
Fedora RPM might be suitable.  The down side of ssmtp is the lack of
queuing should the smart host not be available, not likely but it is
possible the email daemon could crash or be down for maintenance or
other reason.

As far as sendmail, it is simple to switch off the sendmail daemon and
only run the queuing submission agent:

1) edit /etc/sysconfig/sendmail and set
    "DAEMON=no"
2) edit /etc/mail/submit.mc and set
    FEATURE(`msp', `[IP.of.relayhost]')dnl

and of course add an alias for root.

Does anyone on this list have experience running a minimal MTA?  What
other options/software should I be looking at?  Any other insights,
suggestions or insights?

Both the Dom0 and guests are CentOS 5.2.

Thanks in advance,

Brett