120CHAPTER 8: MONITORING ACTIVITY AND STATUS
Troubleshooting Mail When experiencing any mail delivery problems, the first step is to
Delivery Problems examine if the problem is affecting only incoming mail, outgoing, or both. For example, if you are receiving mail, but not sending outgoing mail, it is certain that your Internet connection is working properly or you would not be receiving mail. In this scenario, you may have issues with the firewall or router blocking your outbound SMTP connections or some other problem preventing mail delivery.
Problems affecting both inbound and outbound delivery include the following scenarios:
■Network infrastructure and Communications — The most common scenario in which you are not receiving or sending mail is if your Internet connection is down. This can include upstream communications with your ISP, your connection to the Internet, or your external router. You should also check your internal network infrastructure to ensure you can contact the 3Com Email Firewall from your router or firewall.
■DNS — If your DNS is not working or configured properly, mail will not be forwarded to your 3Com Email Firewall or you will not be able to lookup external mail sites. Check the DNS service itself to see if it is running and check your DNS records for any misconfiguration for your mail services.
■Firewall/Router — If you are having issues with your firewall or router, or if they have been misconfigured, this may inadvertently block mail access to and from the 3Com Email Firewall. For example, SMTP port 25 must be opened between the Internet and the 3Com Email Firewall to allow inbound and outbound mail connections.
■Internal Mail Systems — You may be receiving incoming mail to the 3Com Email Firewall, but mail is not being forwarded to the appropriate internal mail servers (such as Exchange). Also, outgoing mail from the internal servers may not be forwarded to the 3Com Email Firewall for delivery. In these scenarios, examine your internal mail server to ensure it is working properly. Check communications between the two systems to ensure there are no network, DNS, or routing issues. Also check that your internal servers are configured to send outgoing mail to 3Com Email Firewall.
■External Mail Systems — If you have sent a large amount of mail to a particular destination and that mail server is currently down, these messages will queue up in the deferred mail queue to be retried after