We have an application that sends >5000 emails per day to our customers. Some times there will be a burst of 50+ emails generated to multiple users at the same company (i.e. same domain) at the same time. Our current SMTP server creates a connection for each email so we have many connections to one mail server at one time. We then get "421 too many connections" errors from the remote server. The messages then all retry at the same time 10 minutes later -- so it's a nasty loop until the fail after 6 hours. We are going to be migrating to Exchange, but I need to know if this will still be an issue for us in Exchange? How does Exchange handle these situations?

5000 per day is pretty small. Why do the connections fail after only 6 hours? It sounds as if your current SMTP server only allows for a very small number of concurrent sessions. Rich M. - Where are you? :P You can set the max number of connections on the Exchange receive connector easily enough to a number of your choosing ( though the defaults may suffice initially) with the MaxInboundConnection and MaxInboundConnectionPerSource switches http://technet.microsoft.com/en-us/library/bb125140.aspx Set-ReceiveConnector

As as I know when sending the same e-mail to 50 users on the same domain, the exchange just make one connection to the destination server and send the e-mail (if all the recipients are in one message, and not 50 messages with 1 recipeint in each). But you can also limit the number of connections.Yanir Ben-Nun / System Team Leader / IT / IS Professional

Thanks Yanir - it is 50 messages with one recipient each (privacy issues, etc.). The issue is with the destination server limiting the number of connections from a location. We actually just setup an Exchange server and did a proof of concept with one of our trouble customers. Everything worked well so Exchange handles it better than what we currently have.