[Staffslug] postfix dovecot and squirrelmail smtp issues

Has anyone had any joy getting these to work together not via virtual users method. my LEA has recently deleted all the student emails and setup a new email server for my students i am using a cron that runs getmail to download my students emails for them dovecot with a local static uid & gids connects using squirrelmail to access to these locally downloaded emails, whilst getmail downloads any new emails sent to them. My assumption is that i have setup my local smtp server correctly however i seem to be getting these errors 450 4.1.8 me@emailaddress: Sender address rejected: Domain not found i've been going round in circle's at one time i did have it sending emails to local users only ( i could not send to my home email), but i seem to have lost those settings in my fiddling about. I tried turning on squirrelmails smtp settings to connect to the mail.lea.server and trying to authenticate up however this ,ethod requires the imap username to be user@domain instead of just user. and my users login to squirrelmail with user. i could point squirrelmail straight to mail.lea.server and get them to login with user@domain however all the emails that i have stored for them will be lost. I am sure this is 5 minute job for someone who knows what they are doing alas i am not that person. Many thanks in advance Martin i hope i have sent this email to the correct place this time, and not hijacked any threads. If needs be i'll meet someone in a pub with a wifi connection, buy 'em a beer and fix this live