Send Immeditely causes COMMIT_IN_POSTING

Hi All ,

I'm facing the following problem .

In the Tcode for PO in ME23n , after configuring the message type with '4 Send Immediately' and saving it ...it generates a error message the update is terminated and shows error COMMIT_IN_POSTING.

Actually I need to send the smartform as an PDF attachment to an external Email ID and this must be done as soon as I press save in Me23n.

Can u please tell me how to achieve this .

Thanks in advance

Anil