email from moodle

[CarolBooth]

ubuntu 10.04.1 moodle 2.2.2+ postfix
Having trouble sending mail from moodle server. We used to have a zimbra server on site but have now switched to gmail and after reading the guidance at Email setup gmail - MoodleDocs (and failing to make that work) I decided to go back to letting moodle send its own mail and re-installed postfix. It seems that it's still trying to relay via our old zimbra server but I can't find this in any settings to switch it off. Where next?
thanks!
Carol

extract from mail log:

Oct 4 09:49:10 moodle postfix/pickup[29848]: F2DE51401CE: uid=33 from=<AAB7wQAAA==02d5850b849a258bec9f30f3efab9baa@ >
Oct 4 09:49:10 moodle postfix/cleanup[30702]: F2DE51401CE: message-id=<cdb14cb66390272cfa3721f48ec9b92c@moodle.wolsin ghamschool.net>
Oct 4 09:49:11 moodle postfix/qmgr[23021]: F2DE51401CE: from=<AAB7wQAAA==02d5850b849a258bec9f30f3efab9baa@ >, size=791, nrcpt=1 (queue active)
Oct 4 09:49:11 moodle postfix/smtp[30705]: F2DE51401CE: to=<vleadmin@wolsinghamschool.net>, relay=zimbra.wolsingham.internal[10.0.0.6]:25, delay=0.07, delays=0.01/0.01/0.04/0.01, dsn=5.1.7, status=bounced (host zimbra.wolsingham.internal[10.0.0.6] said: 501 5.1.7 Bad sender address syntax (in reply to MAIL FROM command))
Oct 4 09:49:11 moodle postfix/cleanup[30702]: 100F81401D9: message-id=<20121004084911.100F81401D9@moodle.wolsinghamsc hool.net>
Oct 4 09:49:11 moodle postfix/bounce[30706]: F2DE51401CE: sender non-delivery notification: 100F81401D9
Oct 4 09:49:11 moodle postfix/qmgr[23021]: 100F81401D9: from=<>, size=2944, nrcpt=1 (queue active)
Oct 4 09:49:11 moodle postfix/qmgr[23021]: F2DE51401CE: removed
Oct 4 09:49:11 moodle postfix/error[30707]: 100F81401D9: to=<AAB7wQAAA==02d5850b849a258bec9f30f3efab9baa@>, relay=none, delay=0.01, delays=0/0/0/0, dsn=5.1.3, status=bounced (bad address syntax)
Oct 4 09:49:11 moodle postfix/qmgr[23021]: 100F81401D9: removed

[Geoff]

You need to change the 'relayhost' setting in /etc/postfix/main.cf. Either comment it out (in which case postfix will send mail directly) or change it to a working relay that you have access to (your LEA SMTP server or whatever).

[CarolBooth]

Thanks very much Geoff and sorry for slow response to your very fast response (I had an old email address registered with this account)
I had another look in postfix config and definitely nothing there but helpful to know I was looking in the right file!
I think we may have a redirect set up somewhere on our network. Is there a way to find out from my server?
Carol

[Geoff]

from your log file your postfix installation is currently trying to relay via zimbra.wolsingham.internal (IP 10.0.0.6). That server is bouncing the mails because vleadmin@wolsinghamschool.net doesn't exist as far as it's concerned.

[CarolBooth]

thanks, that makes sense. Pardon my ignorance of Postfix but could this happen if there was nothing in the postfix config to make it happen?

[Geoff]

Well that depends, perhaps the better starting point is to ask what you actually want to happen?