Hello to all the experts, 

Recently I tried to add a user to my database but I am getting this error when I send the invitation by email. 

Mail delivery failed via SMTP server 'localhost'.
error: 99
Cannot assign requested address

I am using odoo 10.0 community version. Can someone help me figure this issue out. All your help will be much appreciated as I am a beginner and I would like to get all the help needed from this wonderful forum of experts. 

Thanks, 

Tina