To authorize Combell to send emails on your behalf you will have to include it in your SPF record. The SPF record mechanisms used by Combell are shown below.

For Basic E-mail:

include:_spf.relay.mailprotect.be

For Exchange E-mail:

include:_spf.powermail.be 

For more information on enabling DKIM please contact Combell support team and they will be able to configure DKIM for you.

Create a free OnDMARC account to test your configuration.