When i set up a new account in outlook 2007 i want to download all 1000emails from the server and that goes fine, now is it possible to delete all mails older than 21 days from the server but not from the outlook automatically? Does the option "Save a copy on the server + delete from server after x days" mean delete the mail after x days from the moment the download took place?

thanks in advance

Yes, that is what the option means so your so your issue would solve itself within 21 days ;-)

Otherwise, you'll need to logon to your web based mailbox and delete the messages from there.