Configuring Messages Options
The Messages tab of the
properties of an SMTP virtual server enables you to configure
limitations on messages that are sent through the server. (See Figure 9.)
The first two options enable you to specify the maximum size of a
message (including attachments) as well as the maximum amount of data
that can be sent through one connection to the server. You can also
limit the number of messages sent per connection and to limit the number
of recipients to whom they can be sent. These methods all help reduce
unwanted access to the server and helps preserve resources such as
network bandwidth.
The
most common reasons for messaging failures include incorrect addresses
or domain names entered by the sending user. The Send Copy Of
Non-Delivery Report To option enables you to specify an e-mail address
to which undeliverable mail will be forwarded. The Badmail Directory
setting specifies the path to the folder into which these messages will
be sent. You can review these messages or files to detect undeliverable
mail.
Defining Delivery Properties
When communicating
on the Internet, network routing issues and server failures can cause
service outages. The SMTP standard was designed with reliability in
mind. SMTP servers automatically store a copy of messages while they are
trying to send them to their intended destination. If the destination
server is unavailable, the SMTP server will attempt to retry the
operation. You can manage the details of this behavior through the
properties of the Delivery tab. (See Figure 10.)
The Outbound rules define the intervals at which the server will
attempt to retry the transmission of a message if a failure occurs.
You can also
configure the Delay Notification and Expiration Timeout options for both
the Outbound and Local settings to determine when resending of a
message should end.
It is common for SMTP
servers to send messages through other SMTP servers before they reach
their final destination. Administrators can configure their SMTP servers
to require authentication
before they will relay a message. The Outbound Security command on the
Delivery tab enables you to specify the authentication information to be
used when connecting to another SMTP server. The Outbound Connections
settings specify limits on the number of connections to other SMTP
servers and how long they will remain active.
The Advanced command
provides additional options for managing how messages are processed by
the SMTP virtual server. The options include:
Maximum Hop Count
When messages are forwarded to an SMTP server, the message itself
includes a hop count to record the number of times it has been
forwarded. When a message has exceeded the maximum hop count setting, it
will be considered nondeliverable.
Masquerade Domain
This setting instructs the SMTP server automatically to rewrite the
domain of the From address used for outbound messages. You can use this
setting when you want to ensure that outgoing messages have a consistent
domain name.
Fully Qualified Domain Name
This setting specifies the DNS address of the SMTP virtual server,
based on Address (A) and Mail Exchanger (MX) records. In general, each
SMTP server for a domain should have a unique fully qualified domain
name that includes the server name (for example,
Server01.mail.contoso.com).
Smart Host
When a server name or IP address is defined for the Smart Host setting,
all messages from this SMTP virtual server will be routed through the
specified server. This option is commonly used when multiple internal
servers should route their messages through a specific SMTP server that
has access to the Internet. Using a smart host configuration can save
bandwidth and increase security because only specific servers will
require access to external networks. The Attempt Direct Delivery Before
Sending To Smart Host option instructs the local SMTP server to attempt
to connect directly to the destination SMTP server. If this operation
fails, the message will be forwarded to the designated smart host.
Perform Reverse DNS Lookup On Incoming Messages
This setting instructs the SMTP server to perform a DNS reverse lookup
to verify that the user’s domain matches the IP address in the message
header. By enabling this option, you can reduce or prevent unauthorized
usage of the SMTP server by messages that use inconsistent header
information.
Enabling LDAP Routing
The Lightweight
Directory Access Protocol (LDAP) is the primary standard by which
directory services software can communicate with each other. Examples of
LDAP-compliant directory services are Active Directory and Exchange
Server. You can enable the LDAP Routing tab to configure an SMTP virtual
server to use LDAP queries to resolve to and from addresses in mail messages.
The configuration options specify to which type of LDAP system the SMTP
server will be connecting and the address of the server. Other details
include authentication information for connecting to and querying the
LDAP server.
Managing Security Permissions
You can define which Windows users may manage SMTP Virtual Server settings by using the Security tab. (See Figure 11.)
The list defines which users should be considered operators. Operators
have permissions to change the configuration of the SMTP virtual server.
By default, this includes the Administrators group and the Local
Service and Network Service built-in accounts. You can click the Add
button to include additional users or groups on the list of operators.
