Cisco Cisco Content Security Management Appliance M1070 Mode D'Emploi
C H A P T E R
12-1
AsyncOS 8.3.6 for Cisco Content Security Management User Guide
12
Configuring SMTP Routing
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SMTP Routes Overview
This chapter explains the features that affect routing and delivery of email traveling through the Cisco
Content Security Management appliance, and use of the SMTP Routes page and smtproutes command.
Content Security Management appliance, and use of the SMTP Routes page and smtproutes command.
SMTP Routes allow you to redirect all email for a particular domain to a different mail exchange (MX)
host. For example, you could make a mapping from
host. For example, you could make a mapping from
example.com
to
groupware.example.com
. This
mapping causes any email with
@example.com
in the Envelope Recipient address to go instead to
groupware.example.com
. The system performs an “MX” lookup on
groupware.example.com
, and then
performs an “A” lookup on the host,
just like a normal email delivery. This alternate MX host does not
need to be listed in DNS MX records and it does not even need to be a member of the domain whose
email is being redirected. The operating system allows up to ten thousand (10,000) SMTP Route
mappings to be configured for your Cisco Content Security appliance. (See
email is being redirected. The operating system allows up to ten thousand (10,000) SMTP Route
mappings to be configured for your Cisco Content Security appliance. (See
.)
This feature also allows host “globbing.” If you specify a partial domain, such as
example.com
, then any
domain ending in
example.com
matches the entry. For instance,
fred@foo.example.com
and
wilma@bar.example.com
both match the mapping.
If a host is not found in the SMTP Routes table, an MX lookup is performed using DNS. The result is
not re-checked against the SMTP Routes table. If the DNS MX entry for
not re-checked against the SMTP Routes table. If the DNS MX entry for
foo.domain
is
bar.domain
, any
email sent to
foo.domain
is delivered to the host
bar.domain
. If you create a mapping for
bar.domain
to some other host, email addressed to
foo.domain
is not affected.
In other words, recursive entries are not followed. If there is an entry for
a.domain
to redirect to
b.domain
, and a subsequent entry to redirect email for
b.domain
to
a.domain
, a mail loop will not be
created. In this case, email addressed to
a.domain
will be delivered to the MX host specified by
b.domain
, and conversely email addressed to
b.domain
will be delivered to the MX host specified by
a.domain
.