use the @cloudron/superagent module

src/mail.js

@@ -79,7 +79,7 @@ const assert = require('assert'),
     safe = require('safetydance'),
     services = require('./services.js'),
     shell = require('./shell.js')('mail'),
-    superagent = require('./superagent.js'),
+    superagent = require('@cloudron/superagent'),
     validator = require('./validator.js'),
     _ = require('./underscore.js');