You can make URLs in the current buffer active with M-x goto-address-mode. This minor mode finds all the URLs in the buffer, highlights them, and turns them into buttons: if you click on a URL with Mouse-1 or Mouse-2 (see Mouse References), or move to the URL and type C-c <RET>, that displays the web page that the URL specifies. For a ‘mailto’ URL, it sends mail instead, using your selected mail-composition method (see Mail Methods).
It can be useful to add
goto-address-mode to mode hooks and
the hooks used to display an incoming message (⁖,
rmail-show-message-hook for Rmail, and
for MH-E). This is not needed for Gnus, which has a similar feature
of its own.