This document will explain the procedures for installing and configuring Stunnel, a third party SSL tunneling client to be used if your SMTP server requires SSL. Stunnel is required for WIN-911 V7 as it does not natively support SSL. We have provided an example Stunnel configuration in this article that will using Gmail's SMTP server. While we are using Gmail as an example, please be aware that Google enforces sending limits on Gmail accounts. Currently the limit is 500 emails in a day. If your WIN-911 configuration contains a large number of Email Contacts and/or Alarms, you will need to find an alternative to Gmail. 

Download and Installing Stunnel

Download the latest installer of Stunnel from   

As of the date of this article, stunnel-5.40-win32-installer.exe, is the latest version available.

During the installation process you will come across a command prompt window asking for various organization information. This information is used to create an SSL certificate for Stunnel. If you skip this process Stunnel will not function properly.


Configure Stunnel

You can use Stunnel to configure any SSL enabled server. As we mentioned in the Introduction, we have provided an example using Gmail.

Stunnel is configured with a text based configuration file titled “stunnel.conf”. You can find the file in the directory Stunnel is installed to or from selecting Start > All Programs > stunnel > Edit stunnel.conf.

Once you’ve opened the stunnel.conf file in Notepad you’ll be presented with their default configuration. We don’t need this configuration so you will need to remove it. Do this by highlighting all the text and delete it. You will now have a blank text file, copy only the bold text I’ve posted below and paste it into the configuration file. Save the configuration and now you can start the Stunnel runtime. If Stunnel was running then you’ll need to open the Stunnel GUI and select Configuration > Reload stunnel.conf from the menu bar.

client = yes
accept =
connect =

The accept property is used to specify the host that will accept the connection and the connect property is used to specify the remote host. If you’re using a connection other than Gmail, you should only have to change the  SMTP connect server and port.

Now that you have Stunnel configured you may want to configure it to run as a Windows service. First, you’ll need to install Stunnel as a service by going to Start > All Programs > stunnel > Service install. A successful dialog should appear. You can now find Stunnel in your Windows Services list. Set the service to start Automatically. We suggest rebooting your system and triggering an alarm after you have WIN-911 and Stunnel working to ensure it is functioning properly

Configure Gmail

In order to send email through Gmail using 3rd party email clients, including WIN-911, you must enabled the "less secure apps" feature. You can do this by logging into the Gmail account you'd like to use  and open the Less Secure Apps page, located here,

Select the option to turn on access for less secure apps and you can logout.

Configure WIN-911

Use the following screenshots to configure WIN-911 to use Stunnel.

SMTP Settings


Authentication Settings


Restart WIN-911 and test your settings by sending a Manual Message.


If you are still experiencing a problem with Email, please submit a support request or contact Product Support at 512-326-1011 x3 or toll free in the US and Canada at 1-800-331-8740 x3

Additional support information may be available from Stunnel at