What is a DKIM signature, and how does it help filter emails?
If you run a business in 2025, then email authentication is something that you must take seriously. With around a 341% increase in malicious emails, it’s no longer about the flexibility to focus on cybersecurity; it’s a necessity now.
To make things worse, Gen AI models with no guardrails are offering swift answers to malicious queries. To combat the advanced moves of threat actors and uncensored AI chatbots, organizations must pay special attention to ensure that all emails come from legitimate sources. This can be done by deploying one of the most effective email authentication protocols- DKIM (DomainKeys Identified Mail). This article explores what a DKIM signature is and how it can enhance email security for your business.
DKIM signature- meaning
DKIM is one of the email authentication protocols that enable recipient email servers to verify the integrity of the emails sent from your domain. It helps them understand whether or not the email received has been tampered with during its transit. The core idea of DKIM is based on a digital signature attached to the email header. This DKIM signature serves as a security stamp and is unique in nature. The signature verifies that the email has been sent and authorized by none other than the legitimate domain owner. A DKIM signature can be considered as a cryptographic authentication.
DKIM helps you in places where SPF authentication can’t be filled in. SPF only helps in verifying the legitimacy of the sender. It indicates nothing about the tampering done with the content.
What does DKIM do, and how does it work?
When setting up, DKIM generates a cryptographic key pair. The two parts of this key are a private key and a public key. While the private key is used to create the DKIM signature for outgoing emails, the public key gets published in the DNS (Domain Name System) records.
Here’s how DKIM works:
Sending the email
While sending out an email, the sender’s server attaches a DKIM signature to it. The signature is created using the private key. To make it unique, the signature includes a coded summary of the email content and metadata.
Receiving the email
The recipient email server retrieves the public key from the DNS records.
Signature verification
Next, the recipient email server uses this public to decrypt and verify the DKIM signature.
Authentication check
When the email matches the coded summary, they consider the email as genuine and untampered. In case there is some mismatch, there are higher chances of the email getting flagged, landing in spam folders, or straightaway getting rejected.
What does a DKIM record look like?
A DKIM record is always a type of TXT record that is stored in DNS records. The public key is uploaded to the DNS record, which is later used to verify the email signatures. You may need to take the help of professionals or your IT department to set your DKIM record. This DKIM record consists of the sending domain as well as the DKIM selector.
A DKIM selector is either a name or number that the sender uses to convey to the recipient email server where to find the private key. The signature header is then added to outgoing email messages. It is used to help the recipient email server cross-check the authenticity of the email.
This is what a DKIM record looks like:
selector._domainkey.example.com TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3…”
How to set up and check DKIM
Setting up DKIM can be an intricate process. Here’s how to do it in a step-by-step manner:
1. DKIM key pair generation
First, use a DKIM key generator to create a pair of public and private keys.
2. Adding DKIM record to DNS
Then, get the public key published in the DNS settings in the form of a TXT record.
3. Enable DKIM signing
Next, you will have to configure your email server to sign outgoing emails using the private key.
4. Test DKIM setup
There are tools such as Google Admin Toolbox and DKIM validator that can be used to check whether or not the DKIM is working properly.
Further, for checking DKIM, i.e., to verify if DKIM is working correctly for your domain, here’s what you are required to do:
- Simply send an email to any Gmail account.
- Next, open that email and click on ‘Show original.’ You will find this in Gmail settings.
- Now look for ‘DKIM: PASS.’ This indicates clearly that your email authentication has been successful.
- However, if you see ‘FAIL,’ go check your DKIM settings and DNS records for errors.
Does email deliverability improve with DKIM?
A big YES! DKIM protocol definitely improves email deliverability. Multiple email providers such as Outlook, Gmail, and Yahoo depend on DKIM authentication. Hence, it is advisable to deploy the DKIM protocol to prevent your emails from ending up in spam folders or getting rejected.
This is how DKIM enhances your business email deliverability:
Minimizes spam filtering to a great extent
A valid DKIM signature significantly brings down the risk of emails landing in spam folders.
Enhances credibility
Major email providers trust DKIM-signed emails way more than unsigned emails.
Skyrocket domain reputation
When a domain gets associated with DKIM, it is considered reliable and trustworthy. So there are lesser chances of it getting blacklisted.
Wrapping up!
DKIM is one of the most reliable and popular email authentication protocols that helps prevent email tampering, enhances email deliverability, and thereby improves overall email security. When you add a DKIM signature, you can rest assured that if someone alters the content of the emails you send, they will be flagged. It further strengthens your email defense mechanism when you combine it with SPF and DMARC protocols. If you wish to improve your business email security and deliverability, then do get in touch with our experts and set up DKIM today!