What is the difference between SPF and DKIM?

SPF specifies which servers may send email on behalf of your domain, while DKIM signs the content of the email itself with a digital key.

Do I need both SPF and DKIM?

Yes. It is strongly recommended to use SPF, DKIM and DMARC together to achieve the best possible email security and deliverability.

How do I know whether my DKIM is working?

You can use online DNS tools or analyse the email headers of received messages to see whether the DKIM signature validates correctly.

What is a DKIM record in DNS?

A DKIM record is a TXT record in your DNS containing the public key that the recipient's mail server uses to verify your digital signature.

Can DKIM prevent spam from my email address?

DKIM prevents others from impersonating you (spoofing), which reduces the risk of your domain being abused for spam.

How often should you update your DKIM key?

It is good practice to rotate your DKIM keys at regular intervals, for example once a year or when you change email provider.

What is DKIM? A guide to email authentication

If you work with IT security in an SME, you have probably come across the question what is DKIM. At a time when phishing and email fraud are constantly growing, correct email authentication is essential to protect your company's reputation.

What exactly is DKIM?

DKIM stands for DomainKeys Identified Mail. It works as a digital signature attached to your emails. When you send an email, your mail server "signs" it with a private key. The recipient's server then uses a public key (found in your DNS) to verify that the email really does come from your company and that the content has not been altered in transit.

How does DKIM work in practice?

The process behind DKIM is mathematically founded. When an email is sent, a hash value of its content is generated. This value is encrypted with your private key. When the recipient's server receives the email, it decrypts the signature with your public key and compares it with the received message. If they match, the email is authentic. If not, the email is often flagged as suspicious or rejected outright.

Why is DKIM important for your business?

Protection against spoofing: It becomes significantly harder for hackers to impersonate you.
Improved deliverability: Major providers such as Microsoft 365 and Google prioritise emails with a correct DKIM setup.
Phishing prevention: You ensure that your customers and partners can trust the emails they receive from your domain.

How to check your DKIM setup

It is important to validate your DKIM setup on an ongoing basis. You can use tools such as MxToolbox to see whether your DKIM record is set up correctly in your DNS. If you are unsure how, we at teknisksupport.dk can help review your Microsoft 365 setup or other email solutions.

How SPF, DKIM and DMARC work together

You cannot talk about DKIM without mentioning SPF and DMARC. While SPF states which servers may send email on your behalf, DKIM adds a signature. DMARC acts as the overall "police", telling the recipient what to do if neither SPF nor DKIM validates correctly. Together they form a necessary line of defence for modern email security.

Do you need help with email security?

Does your business need help setting up DKIM correctly or with email security in general? Contact our IT support in Kolding for advice. We also help with hosted spam filtering and optimising your IT infrastructure.