Domino® supports a number of extended SMTP (ESMTP) functions. These include the ability to combine (or pipeline) commands, set the server to check message size before accepting transfer, create a secure TLS connection with another server, and create delivery status notifications in MIME format. You enable or disable each of these options in the Configuration Settings document for the server or servers for which you want to use these extensions.

Procedure

1. Make sure you already have a Configuration Settings document for the server(s) to be configured.

2. From the Domino Administrator, click the Configuration tab and expand the Messaging section.

3. Click Configurations.

4. Select the Configuration Settings document for the mail server or servers you want to administer, and click Edit Configuration.

5. Click the Router/SMTPAdvancedCommands and Extensions tab.

6. Complete these fields, and then click Save and Close:

Table 1. Inbound SMTP Commands and Extensions fields

Field	Enter
SIZE extension	Select one: Enabled - (default) Domino declares its maximum message size to connecting hosts and checks the sending host's estimates of message size before accepting transfer. If the sender indicates that a message to be transferred is larger than the maximum size, Domino returns an error indicating that it will not accept the message. Disabled - Domino does not advertise its maximum message size or check inbound message size before transfer.
Pipelining extension	Select one: Enabled (default) - Improves performance by allowing Domino to accept multiple SMTP commands in the same network packet. Disabled - Domino does not accept multiple SMTP commands in a single packet.
DSN extension	Select one: Enabled - Domino supports incoming requests to return delivery status notifications to the sender for failed, delayed, delivered, and relayed messages. Domino sends delay reports for low-priority messages held until the low-priority routing time to the sender of an SMTP message upon request. Disabled - (default) Domino does not return delivery status notifications for SMTP messages.
8-bit MIME extension	Select one: Enabled - Domino accepts 8-bit messages as is, allowing reception of unencoded multinational characters. Disabled (default) - Domino requires inbound messages containing 8-bit characters to be sent using 7-bit ASCII encoding.
HELP command	Select one: Enabled - (default) In response to the Help command, Domino displays a list of supported commands. Disabled - Domino ignores the Help command.
VRFY command	Select one: Enabled - Domino accepts inbound requests to verify user names. Disabled - (default) Domino denies requests to verify user names. Note: Enabling this command allows people outside your organization to expand group names and to check for valid email addresses in your organization. You may not want to enable this extension for security reasons.
EXPN command	Select one: Enabled - Domino expands mailing lists or groups to show individual recipient names. Disabled - (default) Domino does not expand lists and groups. Note: Enabling this command allows people outside your organization to expand group names and to check for valid email addresses in your organization. You may not want to enable this extension for security reasons.
ETRN command	Select one: Enabled - Domino accepts inbound "pull" requests from other SMTP hosts to transfer messages destined for the calling server. Enabling ETRN support allows for more efficient use of bandwidth resources by allowing a remote SMTP host to request pending messages at the same time it transfers messages to the Domino server. Disabled - (default) Domino does not accept inbound "pull" requests from other SMTP hosts.
TLS negotiated over TCP/IP port	Select one: Enabled - Domino supports the STARTTLS command, allowing it to create an encrypted TLS channel over the SMTP TCP/IP port. Required - Domino accepts inbound SMTP connections over the TCP/IP port only from hosts that issue the STARTTLS command. Disabled (default) - Domino does not allow secure TLS connections over the SMTP TCP/IP port. Note: After accepting the STARTTLS command from a remote server, Domino uses settings for the server's TLS port to govern authentication for the sessions. For Domino to authenticate remote hosts that use the SMTP AUTH command, Name & Password authentication must be enabled for the Domino TLS port. Note: After accepting the STARTTLS command from a remote server, Domino uses settings for the server's TLS port to govern authentication for the sessions. For Domino to authenticate remote hosts that use the SMTP AUTH command, Name & Password authentication must be enabled for the Domino TLS port.

Related concepts
Restricting SMTP inbound routing
Securing SMTP sessions using the STARTTLS extension

Related tasks
Creating a Configuration Settings document
Restricting mail routing based on message size
Stopping and starting the Domino SMTP service
Updating the SMTP configuration
Restricting users from receiving Internet mail
Supporting outbound SMTP extensions
Changing the inbound SMTP port settings

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