If your company uses Mimecast as your third-party filter you should add your sending domain and IP to the Mimecast greylisting, permitted senders and anti-spoofing policies.

Greylisting is a typical check that Mimecast uses to check any brand new inbound mail that has never been seen by Mimecast. Most spam comes from completely new systems and so is treated with caution.

Permitted senders policy is essentially a list of senders that you want to manually allow through the filter because you trust them.

Anti-spoofing policy helps with managing large amounts of spoofed mail.

Configuring a Mimecast policy

The process for putting these in place is almost identical. Below are broad instructions on where to find these policies in Mimecast but we have also included link to the specific articles on Mimecast’s site.

 

1. Log on to the Administration Console.
2. Select the Administration menu item.
3. Select the Gateway | Policies menu item.
4. Select The policy you wish to change.
5. Either select the:
6. Policy to be changed.
7. New Policy button to create a policy.
8. Complete the Options section as required:
9. Complete the Emails From and Emails To sections as required
10. Complete the Validity section as required:
11. Select the Save and Exit button.
12. Complete the Validity section as required:
13. Click on the Save and Exit button.

Configuring Greylist policy

Configuring permitted sender policy

Configuring anti-spoofing policy