While I don't know exactly what would be causing the error, I can give you something to check.
Assuming your running the exact same version of EE and all addons etc, the prime suspect for me would be the PHP modules on the live server being different from production. Just pull up phpinfo on development and live servers (you can get to it from Tools > Utilities > PHP Info.
YOu shouldn't need to go through the whole config, just check the compile commands on each box, look for any that are missing on the development server to the live server and that should give you a hint.
If this doesn't look to be it, best you provide a bit more info on your setup, so version of EE, any email related addons your running if any, in particular any that affect email handling like Escort etc. This will help anyone else that swings by home in on the issue.
Fatal error: Cannot access protected property EE_Email::$_recipients in [...]/third_party/postmark_system_emails/ext.postmark_system_emails.php on line 147