Problem

Custom Email sent through Kinvey has a url link. When this email is received by Yahoo, the url link is not clickable.

Solution

Kinvey is using mustache templates to insert variables, including the url.  

Mustache is applying HTML escaping by default to all variables and it seems that Yahoo mail client does not accept the HTML escaped characters in href attributes and thus is removing the href attribute at all, making it non-clickable.

To overcome this, simply change the double mustache {{url}} to the triple mustache: {{{url}}} which will return the unescaped HTML:

<a href={{{url}}}>{{{url}}}</a>