DKIM is a security check that makes sure email messages aren't changing between when the email is sent and when the recipient receives them. Emails are less likely to be labeled as spam when they pass DKIM checks.
It's not required to be configured but it is recommended.
Here's how to enable DKIM in the Paubox admin panel:
Please note that you will need to add a new DNS record at your domain hosting provider to complete the DKIM configuration so you may want to check if you have that access before completing the steps below.
1) Visit https://www.paubox.com/users/sign_in in your browser.
2) Log in with your Paubox admin panel email address and password. If you don't know what your password is for the Paubox admin panel, click the "Forgot your password?" link.
3) In the left navigation menu, navigate to Overview > DKIM Configuration > Open Settings)
4) Select your domain (or subdomain) from the dropdown menu and click "Generate DKIM Key"
5) Follow the instructions on the page for adding a new DNS record at your domain hosting provider
6) Toggle "DKIM Enabled" to Yes