error 500.phtml

internal server error

and debug mode shown

Message:Invalid argument `$email`File:/home/kapoo/domains/kapooboard.com/public_html/ow_system_plugins/base/classes/mail.phpLine:67Trace:#0 /home/kapoo/domains/kapooboard.com/public_html/ow_system_plugins/admin/controllers/mass_mailing.php(192): BASE_CLASS_Mail->addRecipientEmail('fr0st4rust-@hot...') #1 [internal function]: ADMIN_CTRL_MassMailing->index(Array) #2 /home/kapoo/domains/kapooboard.com/public_html/ow_core/request_handler.php(266): ReflectionMethod->invokeArgs(Object(ADMIN_CTRL_MassMailing), Array) #3 /home/kapoo/domains/kapooboard.com/public_html/ow_core/application.php(330): OW_RequestHandler->dispatch() #4 /home/kapoo/domains/kapooboard.com/public_html/index.php(65): OW_Application->handleRequest() #5 {main}Type:InvalidArgumentException


( It is shown error in some group . Mass mailing error after sent email to member but it is work normal for some new group thai i create it.

How i can solve this problem for both website ?