Valid links

Email open action short links:

Used to record if an email is opened. In email marketing or newsletter you can not rely on particular email clients to send you information about email open action. A solution is to record a resource request like an image download, that will happen if the user uses a WEB email client or it voluntarily requests to download email pictures  (add more picture into your email to trigger the need to download).
The shortcut link of trigger picture is one transparent pixel PNG image.
The link is like http://l91.be/aa0-dGVzdC5tYWlsQHNhbXBsZS5jb20.png 
where:
    - the URL service address is https://l91.be (is short)
    - the link code is between the "/" and "-" (aa0 here)
    - between "-" and ".png" is a BASE64 encoded email address.
    - ".png" is added for server-side reasons and in order to mimic a normal PNG file source.
In the HTML email message body will look like:
<img src="http://l91.be/aa0-dGVzdC5tYWlsQHNhbXBsZS5jb20.png">

The Base64 encoded email address should be added automatically into your email newsletter campaign when a particular email message is created for one email address.

Email link click recording:

To record a click action of a particular user of your newsletter you will need to add the Base64 encoded email address to the link as a query parameter (e). See one sample below.
http://l91.be/aa1?e=dGVzdC5tYWlsQHNhbXBsZS5jb20

These actions should be performed automatically by your newsletter campaign software.