Increase your deliverability with email authentication

Spammers have been increasingly active in recent years. These illegal practices are a nuisance for legitimate email marketers. Countering them requires ever more powerful spam filters, and even legitimate emails can often disappear into the ‘junk folder’. We have provided a solution to address this issue: email authentication.

What is email authentication?

The primary aim of email authentication is to prevent abuse (spoofing, phishing) and to make possible a reliable identification of the sender of an email message, in order to obtain a higher deliverability rate with the major ISPs. By adding certain records to your domain configuration, you can significantly improve the deliverability of your email messages.

Flexmail uses 3 different technologies for this purpose:

SPF stands for ‘Sender Policy Framework’. It is a tool designed to prevent the falsification of the sender’s address on email messages. SPF confirms to the receiving ISPs that the Flexmail servers are authorised to send email messages for your domain.

SPF is used by Google and many others.

Sender ID
Sender ID is a method developed by Microsoft for verifying the sender of an email communication. This technology is comparable to SPF.

Sender ID is used by Microsoft ( – formerly Hotmail – and Exchange) and many others.

DKIM or ‘DomainKeys Identified Mail’ is a technology used to determine the identity of the sender of an email. Both a private and a public key are used for this purpose.

Flexmail signs every outgoing email with a cryptographic private key. This key must match a public key that is saved in a TXT record of the domain. This record confirms to the receiving ISPs that Flexmail email messages can be sent for this domain. This recent technology will become increasingly important in the future.

DKIM is used by Yahoo, Google and many others.

How do you proceed?

Flexmail checks existing records on the basis of the sender’s email address, and automatically generates any missing records for your email authentication.

You then need to pass that information on to the manager of your domain name. You can generate a handy PDF document that contains all the relevant information.

Step 1:
To set up email authentication within your Flexmail account, go to Home > Settings. Among the options, click below on ‘Email authentication’.

The email address will be automatically prefilled as sender address for your campaigns. 

Step 2:
On the next screen you will see three different protocols in a row. For DKIM you need to generate a key. If you have not yet made one up, you can leave the selector on ‘default’. Then click on ‘Generate’.

Step 3:
Once you have generated the DKIM, all you have to do is click below on ‘Generate PDF’. You will receive a PDF document containing all the information about the records to be created. This document can later be given to your domain manager. That way, the latter person has all the information necessary to be able to create the records.


Once your domain manager has created the records, you can always check that everything has been entered correctly using Flexmail’s email authentication. The red toolbar on each record will turn green if the record has been found.

The email authentication is easy to set up. Because the receiver mail servers can confirm that you are a reliable sender, your email communication will be easier to put on a white list, your deliverability will increase significantly.


Are you looking for more tips on how to increase your deliverability? If so, then check out the section of our blog devoted to deliverability.

You can find all sorts of tips on how to write effective subject lines, avoid spam-sensitive words, support your email clients, and much more!