HiWe are using Exchange 2003 SP2 in our organisation...Let's say a message goes from Exchange 1 > Bridghead 1 > Bridghead 2 > Exchange 2Exchange 1 and 2 are mailbox servers.Let's say for some reason Exchange 2 goes down. Is there any sort of re-try period for Bridgehead 2 to keep trying the message? Assuming there is, and this passes without Exchange 2 coming back again, I assume Bridgehead 1 sends an NDR back to the sender...but what happens to the actual message? Does it get stored in a Badmail directory...and does this folder have to be emptied from time to time, otherwise surely over time it would just get full?....and does all this behaviour differ in Exchange 2007 at all?

If one server malfunctions, mail to that server will be queued up for a default period of time of 48 hours. After some time (I think itis 4 hours) users will get notified that mail is in queue.There is noNDR until the 48 hours limit.Exchange 2007 will behave the same. This is also the most normal way of every mailsystem.lasse at humandata dot se, http://anewmessagehasarrived.blogspot.com

Thanks - but what happens to the actual message and attachment? So, say I send a mail with a .doc attachment that cannot be delivered - would the attachment come back to me?Is there a setting in IIS/Exchange to control whether the NDR contains the original mail?

The message that could not be delivered is deleted and a NDR is sent back to the sender.You can however set a limit on the NDR message size.http://technet.microsoft.com/en-us/library/aa996279.aspxhttp://support.microsoft.com/?kbid=308303Do you want the NDR to contain the original message or not?lasse at humandata dot se, http://anewmessagehasarrived.blogspot.com

Q: Is there any sort of re-try period for Bridgehead 2 to keep trying the message? A: Yes. Since exchange 2003 uses link state information for transport routing, if the link between two mail exchanges is down, The 48 hour time period is the default length of time for messages to sit in a queue before a Non-Delivery Report (NDR) is generated and sent back to the user. Like Lasse said, 2 days Q: what happens to the actual message? A: The undeliverable mails wont be saved in order to prevent the Badmail folder from filling up with messages (KB 884068) Q: does all this behaviour differ in Exchange 2007 at all A: Theres no Badmail folder in the exchange 2007. The messages that are determined to be badmail are left in the Pickup or Replay directory and are renamed from .eml to .bad. If .bad message already there, itll rename to MessageName.Date.bad. When badmails exist in your system, related event log will be generated to remind you Q: Is there a setting in IIS/Exchange to control whether the NDR contains the original mail? A: Well, Lasse has answered it. Heres another similar article (KB 555231) Resources: How to Specify How Undeliverable Mail is Managed How to Configure the Replay Directory How to Change the Location of the Queue Database