Make sure you do not just type the URL in your e-mail.
You must hyperlink the URL prior to sending the message. We do link tracking by doing a brief redirect through our servers. We create a special URL when it is hyperlinked and won't be able to do if it's just seen as text. Your tracked links will go through our app and then pass through to the site that you originally linked to.
To be 100% certain that your links are tracked we recommend that you add them to your message using the link formatting tool in Gmail or Inbox:
In Gmail In Inbox