I have a 7.3 smeserver and we have upgrade the workstations to windows 7 and Office 2010. With Outlook 2010 if you have the read receipt ON the read receipt will stay in the Outbox and no email will be send until you remove the stuck emails from the Outbox. If you switch the read receipt to OFF emails will not get stuck and emails will be send. Is this an issue of 7.3 solved in newer versions or it will happens even on 7.5