Procedure

1. Go to Administration → IMSS Configuration → SMTP Routing.
2. Click the Connections tab.
   The Connections screen appears.
3. Specify the SMTP Interface settings.
   • IP address: Select the interface that will connect with your SMTP server.

     Loopback address

     The SMTP server will only listen to the IP address on the local computer.

     All interfaces

     If there are multiple IP addresses on the computer, the SMTP server will listen to any of the IP addresses available.

   • Port: Specify the listening port of the SMTP server.
   • Disconnect after { } minutes of inactivity: Specify a time-out value.
   • Simultaneous connections: Click No limit or Allow up to { } connections and specify the maximum number of connections.
4. Specify the Connection Control settings.
   1. Select Accept all, except the following list to configure the "deny list" or Deny all, except the following list to configure the "permit list”.
   2. Configure the list using any of the following options.
      • Single computer: Specify an IP address, and then click >> to add it to the list.
      • Group of computers:
        1. Select the IP version. IMSS supports IPv4 and IPv6 addresses.
           • For IPv4 addresses, specify a subnet address and mask.
           • For IPv6 addresses, specify a subnet address.
        2. Click >> to add the group to the list.
      • Import from file: Click to import an IP list from a file. The following shows sample content of an IP list text file:
        192.168.1.1
        192.168.2.0:255.255.255.0
        192.168.3.1:255.255.255.128
        192.168.4.100
        192.168.5.32:255.255.255.192
        2001:db8:10ff::ae:44f2
        2001:db8::/32
5. Specify the Transport Layer Security settings:
   1. Select Enable Incoming Transport Layer Security.
      This option allows the IMSS SMTP Server to provide Transport Layer Security (TLS) support to SMTP clients, but does not require that clients use TLS encryption to establish the connection.
   2. Select Only accept SMTP connection by TLS for IMSS to only accept secure incoming connections.
      This option enables the IMSS SMTP Server to accept messages only through a TLS connection.
   3. Click a Browse button next to one of the following:
      • CA certificate: A CA certificate is usually used for verifying SMTP clients. However, IMSS does not verify the client and only uses the CA certificate for enabling the TLS connection.
        Only upload this file if it is provided to you together with the public key. Otherwise, this file is not mandatory for enabling a TLS connection.
      • Private key: The SMTP client encrypts a random number using IMSS SMTP server's public key and an encryption key to generate the session keys.
        IMSS SMTP server then uses the private key to decrypt the random number in order to establish the secure connection.This key must be uploaded to enable a TLS connection.
      • SMTP server certification: The IMSS SMTP server's public key made available to the SMTP clients for generating the session keys.
        This key must be uploaded to enable a TLS connection.
   4. Click Upload to save the file on the IMSS server.
6. Click Save.