Don't auto-add http:// to mailto: and ftp: markdown links

web/react/utils/markdown.jsx

@@ -32,7 +32,7 @@ export class MattermostMarkdownRenderer extends marked.Renderer {
     link(href, title, text) {
         let outHref = href;
 
-        if (outHref.lastIndexOf('http', 0) !== 0) {
+        if (!(/^(mailto|https?|ftp)/.test(outHref))) {
             outHref = `http://${outHref}`;
         }
 

web/react/utils/text_formatting.jsx

@@ -89,7 +89,7 @@ function autolinkUrls(text, tokens) {
 
         if (match.getType() === 'email') {
             url = `mailto:${url}`;
-        } else if (url.lastIndexOf('http', 0) !== 0) {
+        } else if (!(/^(mailto|https?|ftp)/.test(url))) {
             url = `http://${url}`;
         }