SPF Records

SPF Records are an extension to DNS that brings higher anti-spam protection for you as well as recipients of your emails. They are meant to protect you from email forging by defining the list of IP addresses allowed to send emails from your domain.

As Mailkit is sending emails on your behalf and your domain, when SPF records are present and not allowing Mailkit servers to send emails, large amount of emails won't be delivered.

To allow Mailkit in your SPF please add the following to your SPF record:

"v=spf1 ... include:mailkit.eu ..." or add the IP ranges of our mail servers by "v=spf1 ... ip4:217.11.236.80/28 ip4:77.78.106.128/26 ..."

For more information about SPF please visit OpenSPF