We are running Windows Small Business Server (SBS) 2003 with Exchange Server 2003. Our POP3 connector service retrieves email every 15 minutes, and most users receive external email without any issue. However, there are a few users who are not receiving external email. They can send and receive internal email and can send email externally. Senders also aren't receiving a non-delivery report (NDR). What is causing this issue?
One factor that can affect this is whether or not each user configured in the POP3 connector has the same external mail server. If the same server downloads all users' mail, then the problem is likely a mismatch of the username and/or password. It could also be a mismatch of the mail server itself -- between the POP3 connector and the external server.
If the users having problems are hosted on different mail servers, then you need to check with the administrator of that external server and make sure it is configured correctly for POP3 access and does not have any IP address or authentication restrictions.
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