* Added: full support for SendGrid web API & SMTP
* Added: Zapier integration with more options
* Added: automatic retry of failed delivery
* Added: system error notification in admin area
* Added: spam check with Spamassassin
* Added: auto detection of multi-thread support
* Added: full utf8mb4 support
* Fixed: SSL support for bounce handler
* Fixed: bounce handlers and IMAP servers integration improved
* Fixed: open/click tracking not working correctly
* Fixed: bounce detection with more accurate classification
* Fixed: click issue with legacy campaigns
* Fixed: better multi-threading performance
* Fixed: socket issue on old OS
* Fixed: encoding issue with ISO content
