Hi Soumaya
I don't know for which process module/usage ur sending mails for, It will be gr8 if u can elaborate it more. But I can say u one thing which comes from HR module,. check IT0105 with subtype 0010 Email in PA30 t-code whether its maintained or not. Normally for any workflows notifications we maintain first in subtype 0010 & SU01. Below is the screen shot for PA30
Now maintain here ur E-mail Id
Anticipating that this Info
will be helpful
Cheers
Pradyp