Changed default timeout of smtp from 10s to 60s.

Summary:
Our smtp server responded slowly sometimes and reached the timeout, but actually
it had sent the email successfully. The mta then retried and sent duplicated
emails. So changed to a bigger default value.

Test Plan: Tested in our deployed and it worked

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8852

Author: yehangjun

externals/phpmailer/class.phpmailer.php

@@ -221,7 +221,7 @@ class PHPMailer {
    * This function will not work with the win32 version.
    * @var int
    */
-  public $Timeout       = 10;
+  public $Timeout       = 60;
 
   /**
    * Sets SMTP class debugging on or off.