To allow Sendloop to send emails on your behalf, you will have to add them to your SPF record. The SPF mechanism used by Sendloop is shown below.
You can configure DKIM for your domain by creating a TXT value called s1._domainkey which contains the value provided on your Settings / Sender Domain Authentication page.
For more information please click the button below.
Create a free OnDMARC account to test your configuration.