Accidently clicked deny when "Messaging is sending a large amount of messages...." popped up

[Jethro Tull]

Accidently clicked deny when "Messaging is sending a large amount of messages...." popped up

I accidently clicked deny when the "Messaging is sending a large amount of messages...." message popped up. I can't seem to find a way to re-enable the app. Can anybody help me?