Hi Namsheed,
Please check this Transaction code :- LSO_PP40 ( After Executing you can check whether sender & receiver mail Address is maintained or not )
Goto PP01 maintain Info Type Mailing for Org Unit (Mail id - for Sender) or you can maintain in SUO1.
Employee - PA30 Maintain Infotype 105 & Subtype 0010 (Mail id - for Receiver )
After Successfully performing LSO_PP40, Check SOST for Mail Notifications , check with Basis if not displaying
Regards,
Krishna