Hi Alhussien
Please refer to the note as supplied from SAP Inbox regarding email set-up. Although specifically geared for the Agent Inbox, it has a lot of tips on email set-up.
The is referred to as the FAQInbox.
In addition to check the transaction SOST, to see if you emails have indeed be generated. Check the status of these emails...has a send attempt been made, is there an error condition.
Regards
Arden