Mimecast DKIM Setup

Mimecast DKIM Requirements

To configure DKIM for your domain in Mimecast, follow the steps below. This process helps ensure your email is properly authenticated and protected against spoofing:

1. Once logged in, click the “Administration” dropdown, select “Gateway” and click “Policies”
2. Now click the “Definitions” dropdown and select “DNS Authentication – Outbound“.
3. Click “New DNS Authentication – Outbound Signing” to create a new DKIM policy.
4. Fill in a description and select “Sign outbound mail with DKIM”. A domain needs to be selected and so click “Lookup” next to “Domain”.
5. Select your domain by clicking “Select” in front of your chosen domain.
6. Select either “1024 bits” or “2048 bits” as your DKIM Key Length. We recommend choosing “2048 bits” for more secure encryption.Click “Generate”.
7. Your new DKIM key has been generated successfully.
8. Once generated, you can add your DKIM key under domains in Sendmarc if you are a Sendmarc customer or directly in your DNS. Next, under “Policies” select “DNS Authentication – Outbound” by clicking anywhere on the line when highlighted in Blue.
9. Add a new Policy for Outbound Signing and use the following values:
   

   Policy Narrative	DKIM Outbound
   Select Option:	DKIM
   Addresses Based On:	Both
   Applies From:	Email Domain
   Specifically:	[YOURDOMAIN.COM]
   Applies To:	Everyone
   Enable / Disable:	Enable
   Set priority as perpetual:	Always On

   

10. Go back into Mimecast and click “Check DNS” to verify that your DNS has been added to your hosting environment successfully.