3Com 3CR3MFA-92, Руководство пользователя

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Troubleshooting Mail
Delivery Problems
When experiencing any mail delivery problems, the first step is to
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