SPF
To allow Evolutive to send emails on your behalf, you will have to add them to your SPF record. The SPF mechanism used by Simplelists is shown below.
include:mail.evolutive.co.uk
DKIM
To enable DKIM please contact Evolutive support and ask them to enable this for you and they will provide you with the necessary DNS records.
Create a free OnDMARC account to test your configuration.