When 3CX PhoneSystem needs to deliver email notifications, the SMTP mechanisms allowed can either be unauthenticated or authenticated using clear text.

Some SMTP servers may be configured to allow only TLS or SSL exchange. You can achieve this using the following procedure:

1. On the 3CX machine you will need to install the SMTP Server available as part of the IIS installation procedure. This is done from the Control Panel > Add/Remove Program > Windows Components. Under the ‘Internet Information Services’ enable the ‘Simple Mail Transfer Protocol’ checkbox.
2. Once installed you may load the SMTP configuration from the Control Panel > Administrative Tools > Internet Information Services, and right click on ‘Default SMTP server’ and select ‘Properties.
3. Navigate to the ‘Access’ tab and click on the ‘Relay’ option. Set IIS SMTP to allow relay from your PBX machine. You can add both ’127.0.0.1′ as well as the internal IP address of the 3CX machine.
4. Now click on the ‘Delivery’ tab and access the ‘Outbound Security’ options.
5. Set “Basic Authentication” and enter the credentials for the email account you wish to send email as.
6. Enable the “TLS Encryption” option and OK the settings.
7. Click on ‘Advanced’, and in the ‘Smarthost’ field enter the FQDN or IP address of the SMTP server which requires you to use TLS or SSL.
8. Apply the changes made.
9. Load the 3CX Management Console and navigate to the Settings > General node, and click on the ‘Mail Server’ tab.
10. In the ‘Mail Server’ Field enter the IP address of the IIS machine running the SMTP component installed as described above. Typically this will be on the same machine as the 3CX PhoneSystem, so in this case “127.0.0.1″ will be sufficient.
11. In the ‘Reply Address’ enter an email address that is recognized by SMTP component installed as described above.
12. Apply the changes made to 3CX.