How do I set an SPF entry?

The SPF (Sender Policy Framework) is a spam protection procedure used for sender authentication. Additional information is stored in the DNS records of a domain in the form of SPF records. These additional SPF records in the DNS contain detailed information about the sending mail servers.


The receiving mail server can use the SPF-record of the domain to check whether the received e-mail from comes from an authorized mail server, or from an unauthorized server. 

In the latter case, the email can be identified via SPF spam protection and declared as SPAM.

Please set a TXT entry for this. The value must be entered without quotation marks.


How does SPF work?

Providers such as GMX, 1und1 and have tightened the conditions for accepting e-mails. Only mails with the same sender address and actual dispatch domain will be accepted.

This may result in the following error:

550-Requested action not taken: mailbox unavailable 550-Reject due to SPF policy. 
550-The originating IP of the message is not permitted by the domain owner.

So for example, if you send from your mail address to and there redirecting to your GMX mailbox leads to the problem mentioned above.

Since the sender domain is from (original sender "") and SPF is used there, the following is true and the email is to be forwarded to "" again, it does not work.

In this case, GMX sees the sender "", checks the SPF and provides 

that ( is not allowed to send an email for a GMX email address because of the SPF entry.

Checkdomain can unfortunately not change this.

Whoever is affected by such SPF rejects can accept this - after all, the will of the sending provider is enforced, who has expressly prevented these redirects - or he can contact the sender and/or provider 1und1/GMX/ for an

Discuss whether such settings are useful or helpful and how to deal with the e-mails that can no longer be delivered.


Step 1

On our homepage at, click on My Login at the top right and select "Customer Area" to log in.

You will reach the login form by entering your customer number or e-mail address and your customer password and then clicking on the "Login" button.


Step 2

You are now in your customer area. In the left navigation click on the navigation point "Domains".


Step 3

In the domain overview, select the domain for which you want to change the IP address. Click on "Configuration" for the desired domain.


Step 4

Click on the menu item "Checkdomain Nameserver" on the detail page of the desired domain.


Step 5

In the following input mask, set the entry for all mail proxies (mx -all) for professional settings, as shown here.

An explanation of the SPF syntax can be found here.


Then click on the "Save" button to confirm your entry.


Important note!

The nameservers are managed independently.

The data is saved on the name servers immediately. It can take approx. 2 - 6 hours for the change to take effect on the name servers.


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