How to send email alerts from CRM module for Activities associated to an opportunity?

Hi all,

My customer is using CRM Module , through P90CB020 - Manage Opportunities they would like the system to send email alerts when adding activities to the Opportunity and assign them to individual employees. I have set up the employees with their corresponding email addresses but they are not receiving any email on their personal Inbox (Outlook). Instead of this they receive notification alerts on their Personal In Basket tray on the Work Center. Is this working as designed or is there any possibility to send email alerts to an external email address?

Thanks in advance for your help.