Exchange not sending mail to the correct recipient addresses when one of the addresses is incorrect

Question

Hi,
I am creating an email msg programatically and sending to the exchange server.
When all the recipient addresses are correct, the mail is sent successfully.
But if one of the addresses is incorrect, the server gives a "550 5.1.1 User unknown" error and theemail msg is not being sent to the correct addresses as well.
When this is tested via Outlook, the mail is sent to the correct addresses and there is an error mail from the server stating that the mail was not sent to the incorrect address, this is the expected behaviour.
What needs to be done to get the expected behaviour? There must be some alternative setting being used by outlook.

Answer 1

Hi,
What you describe can happen if the AntiSpam Agents has been installed
and Recipient Filter Agent is enabled on Mailbox Servers.
Recipient Filter agent
Although the Recipient Filter agent is available on Mailbox servers, you shouldn't configure it. When recipient filtering on a Mailbox server detects one invalid or blocked recipient in a message that contains other valid recipients, the message is rejected.
From:
http://technet.microsoft.com/en-us/library/jj218660(v=exchg.150).aspx#Mailbox
Martina Miskovic