Mary sent out a Capital Call Notice from DX and received several bounce backs with a 550 Anti-Spoofing  - Inbound not allowed notifications.
She was able to confirm that 58 messaged didn’t make it to its recipients.
 
 
Check Mimecast to find out what IP’s are causing the Anti-Spoofing Lockout.
 
 
FIS sometimes adds new IP address used for sending emails. Since these are not whitelisted in Mimecast, we get behavior above.
To fix this we have add said IP address to our Mimecast Policy.
  1. Log on to the Mimecast Administration Console.
  2. Navigate to Gateway | Policies.
  3. Click on Anti-Spoofing. A list of policies is displayed
 
In this case, we added: 148.163.157.52 and 148.163.159.6.
 
We have to login to finance-win10c PC as x1sa. Open Reporting Mailbox from Browser and check every single bounce back to find out what recipients failed to receive the notice.
Provide this list to Mary so she can re-send from DX.
 
Thanks,
 
Audel Barocio | IT Support | 650-233-5766