In order to start signing your emails sent via Mandrill with DKIM keys, you need to manually setup DKIM for Mandrill. Complicated as it may sound, the process is quite simple. DKIM authentication helps encrypt email messages with a private key that is checked against a public key in your Valimail Enforce configuration to verify email sources.
Enable DKIM signing for your domain in Mandrill
Note: First off you need to add your domain to Mandrill.
1. Open your Mandrill account and go to Settings > Domains.
2. Enter your domain name and click on Add button.
3. After adding your domain, for setting up DKIM for mandrill click on View DKIM Settings,
You will find the DKIM record that contains the DKIM selector (mandrill) and the designated key value that you need to publish in Valimail Enforce.
4. Add the DKIM key in Valimail Enforce. Go to your domain's Configuration page in Valimail Enforce and publish the newly created DKIM key.
a. Click on Add a DKIM key and fill in the info from the newly created Mandrill key and then click Add.
5. After publishing the TXT record in Valimail Enforce, click on the Test DNS Settings button in the Mandrill management console and check for a verification mark against your record.
6. Once the DKIM key is validated, you will be ready to send authentication emails on behalf of your domain, using Mandrill.