Hello Our setup is: Exchange 2007 Mailbox server (Mail1) > Exchange 2007 Hub Server (Hub1) > SMTP Gateway > INTERNET > Partner's SMTP Gateway (Partner1) Partner1 has an issue and is not accepting new email. 1. Will outbound email from our organisation be queued on Hub1 or our SMTP Gateway? 2. How often is the retry period and where is this set? 3. At what point will an NDR be generated and where is this set? 4. What happens to the message when the NDR is generated?

1. Yes for a limited amount of time. Look here, http://technet.microsoft.com/en-us/library/bb124238.aspx, especially the MessageExpirationTimeout property. But would that be a good thing for your users? They may think that mail is being delivered whereas it's just being held. If you have an SMTP gateway (smart host) then you'd have to configure this on it instead because your hub transport server will deliver everything to the smart host, and that delivery will be successful. The smart host would then time out trying to talk to the destination server. 2. The default is 2 days, but you could bump it up to hold messages longer. 3. At the end of the expiration period. 4. It is dropped and the NDR returned. Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Hi, I just make some modifications about the second question: >2. How often is the retry period and where is this set? The MessageRetryInterval parameter specifies the retry interval for individual messages after a connection failure with a remote server. The default value is 1 minute. And you can set it. But Microsoft recommends that you don't modify the default value unless Customer Service and Support advises you to do this. Hope this helps. ThanksPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.