1.  Log into https://login.mimecast.com using your windows login info
  2.  select 'mimecast personal portal'
  3. select circle with face in top right hand corner -
  4. Select 3-dot menu on left of screen -
  5. To add an email/domain to the safesenders list select the 'permitted option'
  6.  To Add an email/domain to the blockewd list select 'Blocked'