Routing mail over transient connections

Sites that do not have permanent connections to the Internet, or to other servers on the Domino® network, can send and receive messages over a transient connection, such as a network dialup connection.

About this task

For example, an organization that does not have a constant connection to the Internet might use a remote mail server at its ISP to hold mail until a local mail server calls in to the ISP server to retrieve or "pull" pending messages from the ISP server. If the ISP mail server supports the SMTP ETRN command, you can configure the Domino® server to "pull" mail over SMTP. A local Domino® server can also use Notes® routing protocols to pull messages from a remote Domino® server over a Notes® Direct Dialup connection.

Note: Support for dialup modem (X.PC) connections is not available on Domino® 8.5 and greater servers.

Setting up Domino® to pull mail from a remote server

About this task

By default, when a local server initiates a connection to a remote server, it uses the connection to push messages to the remote server. The local server does not "pull" pending messages from the remote server. Instead, the local server only receives mail from the remote server when the remote server initiates a connection to route those pending messages. To change this default behavior and have the local server retrieve messages from a remote server during the same session in which it sends messages to the remote server, set up the local server to send a "pull request" to the remote server.

When the local server is configured to send a "pull request," it sends a message to the remote server requesting that the server deliver any messages it has pending for the local server. The remote server receiving the pull request can be any SMTP host; it does not have to be a Domino® server. When the remote server receives the "pull request," it checks its mail queues for any messages pending for the initiating server and starts the processing necessary to transfer those messages.

If you are using SMTP routing, you must make sure that ETRN protocol extension has been enabled on the other server (the one receiving the "pull request"), or it will not be able to receive the pull request. Also the remote server must be able to resolve the DNS host name of the initiating server to an IP address to ensure that the messages can be sent. Generally, ETRN requires that the initiating server has a static IP address, which is available in DNS to the server holding the pending messages.

Note: Some ISPs use DHCP to assign a host a new IP address whenever it connects. If the remote system assigns a new IP address every time you connect, do not configure dialup systems to use pull routing.

When configuring dialup routing, you can indicate how long the initiating server keeps the line open to allow the remote server to establish a connection. This is useful to prevent the initiating server from hanging up the line before the remote server is able to attempt to transfer any pending mail. The initiating server sends a pull request, then pushes any messages it has for the remote server, and then waits for any messages pending from the remote server.

When sending a pull request, the initiating server can also request messages for other servers, domains, hosts, or any queue name within your organization for which the initiating server is responsible.

The ETRN command

About this task

With ETRN support, a dialup SMTP host can notify an SMTP server holding messages for it when to deliver those messages. ETRN enables servers to use bandwidth resources efficiently, because the dialup host sends and receives mail during the course of a single session.

ETRN stands for Extended Turn and is an SMTP service extension command, defined in RFC 1985. that provides improved security over the SMTP TURN command, originally defined in RFC 821. The TURN command allows hosts involved in a SMTP session to reverse their respective roles, so that, for example, if Server1 is sending an SMTP message to Server2, Server1 can issue the TURN command so that Server2 then becomes the sender and Server1, the receiver.

However, because the TURN command has no mechanism for verifying the identity of the calling host, use of the command poses a security risk. A malicious user who spoofs the identify of a server can falsely appear to belong to a someone else's Internet domain and then use the TURN command to retrieve messages intended for that domain.

The ETRN command plugs this security hole by redefining the sending and receiving roles during the course of the SMTP session. For example, after Server1 issues the ETRN command to Server2, ETRN instructs Server2 to open a new SMTP session with Server1. Because Server2 has to resolve the name of Server1 to an IP number in the DNS, Server2 is more likely to open a new SMTP session with the correct machine.

For Domino® to use ETRN to retrieve new mail over a dialup connection, your ISP must support this command. Check with your ISP to verify whether they support this command or not. You can also verify support for the command by establishing a telnet connection to port 25 of the ISP's SMTP server. After the SMTP session starts, type EHLO and press Enter. The response from the ISP's SMTP server indicates whether the server supports ETRN.

To set up a server to route mail over a transient connection


  1. For SMTP routing, on the Router/SMTP Basics tab of the Configuration Settings document for the sending server, enable SMTP for messages sent outside the local Internet domain.
  2. From the Domino® Administrator, click the Configuration tab and then expand the Messaging section.
  3. Click Connections.
  4. Click Add Connection.
  5. On the Basics tab, complete these fields:
    Table 1. Basics tab fields



    Connection type

    Choose one:

    Network Dialup - Choose this option for servers that will route mail over SMTP using this dialup connection. You can also use this option for NRPC routing.

    Notes® Direct Dialup - Choose this option only for servers that will use this connection to route mail over NRPC to another Domino® server.

    Source server

    The Notes® hierarchical name of the local Domino® server initiating the routing request, for example, SMTP/East/Renovations.

    Source domain

    The Domino® domain of the source server, for example, RenovationsEast

    Use the LAN port(s)

    For Network dialup connections, enter the port name for the Domino® TCP/IP port on the local server.

    Use the port(s)

    For Notes® Direct Dialup connections, specifies the name of the communications port that the source server uses.

    Destination server

    The name of the Domino® server, or SMTP server to which you want to route mail.

    For SMTP routing connections to an ISP server, enter the host name of the ISP server, for example, Depending on the requirements of your ISP, the specified host can be used for outbound mail, inbound mail (using ETRN), or both. If the host is used for outbound mail, enter the same host name on the Router/SMTP - Basics tab of the Configuration Settings document, in the field Relay host for messages leaving the local Internet domain.

    Destination domain

    For routing to Domino® servers over Notes® routing, enter the Domino® domain of the destination server.

    Leave this field blank when configuring SMTP routing to an ISP server.

  6. On the Routing and Replication tab, complete these fields, and then click Save & Close:
    Table 2. Routing and Replication tab fields



    Routing task

    Select Mail routing

    Router type

    Choose one:

    • Push/Wait - Select this option when the destination server is used for outbound mail only, and initiates the connection to the source server. After the source server establishes the dialup connection, it waits to receive a connection from the destination server. When the destination server connects and issues a "pull request," the source server then pushes any messages pending for the remote server.
    • Push Only - (default) Select this option if the destination server is used for outbound mail only. The source server calls the destination server and sends messages queued for that destination. You'll need to create a separate Connection document to the server used for inbound mail.
    • Pull Push - Select this option if the ISP host to which the source server connects is used for both inbound and outbound routing. The source server calls the destination server, pushes, or sends, any pending messages for that destination, and then "pulls" messages from the destination server (actually, the calling server issues a request to the other server to push messages back to it). The destination server pushes any pending messages back to the source server. If you select this option, you must specify whether the source server issues the pull request using Notes® routing or SMTP.
    • Pull Only - Select this option if the destination server is used for inbound mail only. The source server calls the destination server and issues a pull request (a request for the other server to push back messages). The destination server pushes any pending messages to the source server. You'll need to create a separate Connection document to the server used for outbound mail.

    Pull routing request protocol

    Choose one:

    • Notes® RPC - The server makes the pull request using Notes® Remote Procedure Calls.
    • SMTP - The server makes the pull request using SMTP. Select this option for SMTP connections that support ETRN.
    Note: When the destination server is a Domino® server, the protocol specified in this field only applies when the Router type is set to Pull Only. By contrast, if the Router type is set to Pull/Push, the sending server always uses the same protocol to issue the pull request that it used to transfer messages to the destination server.

    Request the following when issuing a pull request

    Specifies the servers, hosts, or domains on whose behalf the source server issues a pull request. As a result of the request, the remote server sends all messages it is holding for the specified entities. Choose one or more of the following:

    • Source server name (both Notes® and Host) - (default) The source server requests that the remote server transfer any messages addressed to recipients on the source server. The source server receives messages for addresses that specify either the Domino® server name or the DNS host name (for example, CN=Server/Org=RENOVATIONS or
    • All local primary Internet domains listed Global Domain(s) - (default) The source server requests that the destination server transfer all messages it is holding for recipients with addresses in the primary Internet domain named in the source server's Global Domain document (for example,
    • All alternate Internet domain aliases listed in Global domain(s) - The source server requests that the destination server transfer all messages it is holding for recipients with addresses in any of the Internet domain names listed in the source server's Global Domain document (for example,,,
    • The following servers/domains/hosts - The source server requests that the destination server transfer all messages it is holding for recipients in the specified Domino® servers, Internet domains, or DNS host names. If you select this option, list the specific servers, domains, or hosts on whose behalf the pull request is made. Use this option if the remote server requires the calling server to use a specific syntax or name when sending the ETRN pull request to initiate message transfer.

    Pull router timeout

    The number of seconds that the calling server waits for the answering server to respond to a pull request before disconnecting. The default is 30 seconds.

  7. For outbound SMTP connections, configure other servers on the local network to use the dialup system as a relay.
  8. The change takes effect after the next Router configuration update. To put the new setting into effect immediately, reload the routing configuration.