MailEnable Enterprise Guide
Services and Connectors / SMTP Connector / SMTP - Inbound
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    SMTP - Inbound
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    Port Settings

    SMTP Port:

    SMTP service listens on port:

    Determines the port the SMTP service is to listen on. The default is 25. Inbound SMTP connections from remote servers expect the mail server to be listening on port 25, but some proxy or gateway software may require this to be changed.

    Requires SSL:

    Enables SSL certificate encryption for the port.  Please refer to Server Configuration - Secure Sockets Layer (SSL) encryption for information on how to enable SSL for the server.

    Requires connections to authenticate before sending email:

    When this option is enabled all inbound connections will be forced to authenticate on the default SMTP port before being able to send a message to a locally hosted mailbox.

    Authentication Mode

    Always allow authentication

    This port will allow authentication attempts.
    Never allow authentication This port does not allow any authentication.
    Only allow secure authentication (using SSL or TLS) Authentication is only allowed if the connection is secure.

    Submission Port:

    The submission port is an alternate port to the default port 25. It is common to run another port for users to connect to, since many are blocked from connecting to mail servers on port 25 (which is done to reduce spam).

    Additional Ports:

    You are able to configure extra ports as needed, with the same options as the standard port.


    Advanced Settings

    Maximum number of concurrent connections:

    The number of connections that will be available for remote servers and email clients to connect to.

    Advertised Maximum message size:

    Entering a value here will inform remote mail servers and email clients of the maximum size of an email that should be sent to the server. The size is represented in bytes. Clients or remote mail servers may ignore the value. A size of 0 means that there is no limit on message size.

    Enforce this message size:

    Checks each inbound message size after it is received. If it is over the limit, it will be deleted and an error returned to the remote server or email client that is trying to send..

    IP Address Connection Restrictions

    Access Control

    Specify who can connect to the email server. Specify a list of IP addresses that are either banned from connecting, or are the only ones allowed to connect. Use the * character as a wildcard.

    Inbound IP Bindings

    Select the IP addresses that the SMTP service will be bound to. On a multi-homed machine it may desirable to only listen to connections on particular IP addresses. ‘Always bind the service to all available IP addresses’ will allow connections on all IP addresses that are configured for the machine.

    Allow IPv6 client connectivity  Enabling this option will will allow connections from clients using IPv6 addresses.
    Enable TLS The Transport Layer Security (TLS) protocol allow clients to connect to the SMTP service over the standard port and then negotiate for a secure transaction. TLS is only available on inbound connections. The SMTP connector will use the SSL certificate that has been configured for the server.