SPF Record
SPF (for Sender Policy Framework) is a specific type of TXT DNS record added to the DNS records of your domain name, which publicly shares the IP addresses authorized to use that domain name to send emails. This allows the recipient to automatically check whether the IP address of the server sending an email claiming to come from your address is actually one of the IP addresses authorized by the domain.
If your email address is hosted by an external mail service, you'll need to contact your provider directly for further information.
If necessary, add the following record:
@ 10800 IN TXT "v=spf1 include:_mailcust.gandi.net ~all"
If you have a Gandi-hosted site that sends emails:
@ 10800 IN TXT "v=spf1 include:_spf.gpaas.net ~all"
If you send emails via a domain AND Gandi Web Hosting
@ 10800 IN TXT "v=spf1 include:_mailcust.gandi.net include:_spf.gpaas.net ~all"
Important
There can only be one TXT record present for SPF, if you need to configure several email services (for a newsletter, for example) you will need to add the latter to the existing SPF.
For example, if you use Gandi's email servers along with your own email servers, your SPF record would look like this:
@ 10800 IN TXT "v=spf1 include:_mailcust.gandi.net include:_spf.example.com ip4:217.70.176.0/21 ip6:2001:4b98:c::/48 ip4:217.70.184.158 ip4:217.70.185.10 ip4:217.70.186.165 ip4:155.133.132.131 ip4:155.133.138.131 ptr ~all"