Calling function module in background task

Hello,

There is one function module which is called in background task. Is there any chance that background task is not created and function module is not executed. That function module is supposed to send some outbound message. The FM is called in one user exit. I don't have any idea as why it is called as background task. The probem is that this message is not getting send sometimes.(sometimes it gets send ). Because of this I am not able to make any conclusion.

Please respond if anyone has come across such scenario before.

Thanks in advance,

Minal