The Supreme Court of Canada in Crookes v Newton held that the mere linking to a web site that contained defamatory material did not make the linker liable for defamation. Adding content to the link might change that result.
The Supreme Court of British Columbia has recently held, however, that offering a link to an email program (e.g. ‘mailto:’) on a web page that contains defamatory material constitutes republication of that material, apparently whether or not anyone used it.
Weaver v Corcoran 2015 BCSC 165 (CanLII)
Here is the main passage on that point:
. . . [more]
 The invitation to email the