Hi,I've been trying to solve this problem with Exchange Server 2007 on Windows Server 2008.Occassional messages are being stuck in the mail queue with the error:Last Error: 430 4.2.0 STOREDRV.Deliver.Exception:MapiExceptionADNotFoundThis seems to affect all mail from certain addresses which cannot send mail to any email account on our Exchange.I can't find any other instances of this error message posted online.Please help!!Stuart

Hi Stuart, From your description, I understand occasionally, the message stuck in the queue with error MapiExceptionADNotFound. In addition, the issue occurs when the message sent to random recipient. I would like to explain the error means that Exchange could not find related object from Active Directory. It usually occurs when the AD is not prepared correctly, and Exchange lack permission to read the AD object. Nevertheless, from your description, the issue occurs occasionally. Therefore, I suggest you check the issue through the following aspects: 1. If you have several DC exists in the environment, please check whether AD replication issue exists 2. Check connectivity between the Exchange Server and DCs. 3. Check event log on Exchange for related erro event. Please also notice the AD related event. Mike