In our Exchange 2003 environment, we have two servers which act as our Hub servers. All of the applications use these Hub servers. We recently received complaints from some of the application owners that the mail delivery getting delayed very much. On investigation we found that some application is generating huge number of mails due to some application specific issue. When we do message tracking we are able to see this info. But none of the queues on the server show these mails. Can anybody help to explain what could be the cause? We found that the sender mail address and recipient’s mail address of these mails do not actually exist. So in this case where such mails sit, where source and destination emails address do not exist. Half of these flooded messages are NDRs. These NDRs are also not found in any of the queues. Only when we do message tracking we are able to find the info. Thanks for your help! Regards Jayasimha Jayasimha Puppala

NDRs that aren't delivering would normally be seen in the queues. If they are not, and only show when you restart the transport service for example, then that is usually a sign of third party interference. AV scanning something it shouldn't be is the usual cause. Simon.Simon Butler, Exchange MVP. http://blog.sembee.co.uk , http://exbpa.com/

Do not accept messages for addresses that do not exist in your org and you will be amazed how much that improves things. It's really that simple! If you can't see them in any visible queue, they may be in the temp SMTP database. In which case, a restart the IS and Routing Engine and SMTP service is usually required to surface those and get rid of them. Regardless, follow the instructions below for Exchange 2003 if your current anti-spam product doesnt allow you reject messages destined to accounts that do not exist in your org. http://support.microsoft.com/kb/823866 Create a recipient filter When you use recipient filtering, you can prevent messages from being delivered to e-mail addresses that exist in your organization, and you can filter messages that are directed to e-mail addresses that do not exist in your organization. Recipient filtering only applies to messages that come from anonymous connections. To create a recipient filter, follow these steps: Start Exchange System Manager. Expand Global Settings, right-click Message Delivery, and then click Properties. Click the Recipient Filtering tab. To filter e-mail based on a particular e-mail address, click Add, type the e-mail address, and then click OK. To filter messages that are directed to e-mail addresses that do not exist in your organization, click to select the Filter recipients who are not in the directory check box