What is DKIM?
DomainKeys Identified Mail (DKIM) is an email authentication method that uses cryptographic signatures to verify that an email was sent by an authorized server and hasn't been modified in transit.
DKIM (DomainKeys Identified Mail) is an email authentication protocol that allows the sender to digitally sign their emails. When you send an email with DKIM enabled, your mail server adds a cryptographic signature to the email header. This signature is created using a private key that only your server knows.
When the recipient's mail server receives your email, it retrieves your public key from your domain's DNS records and uses it to verify the signature. If the signature is valid, it proves two things: the email genuinely came from your domain, and the email content hasn't been altered since it was sent.
DKIM works alongside SPF and DMARC to form a complete email authentication system. While SPF verifies which servers can send email for your domain, DKIM verifies the email content itself. Together, they significantly reduce the risk of email spoofing and phishing attacks.
Why DKIM Matters
Without DKIM, anyone could forge emails that appear to come from your domain. This makes your customers vulnerable to phishing attacks and damages your brand reputation. Major email providers like Gmail and Microsoft use DKIM as a key factor in determining whether to deliver your emails to the inbox or spam folder. Emails without DKIM signatures are increasingly likely to be filtered or rejected entirely.
How Ark Handles DKIM
Ark automatically configures DKIM for all your sending domains. When you add a domain in Ark, we generate a unique DKIM key pair and provide you with the DNS record to publish. Once verified, every email you send through Ark is automatically signed with your DKIM key, ensuring maximum deliverability.
Frequently Asked Questions
How do I set up DKIM for my domain?
To set up DKIM, you need to generate a public/private key pair, publish the public key as a TXT record in your DNS, and configure your email server to sign outgoing emails with the private key. With Ark, this process is automated—we generate the keys and provide you with the exact DNS record to add.
What happens if DKIM verification fails?
If DKIM verification fails, the receiving server may mark the email as suspicious, send it to spam, or reject it entirely. The action taken depends on your DMARC policy and the recipient's email provider settings.
Can I have multiple DKIM keys for one domain?
Yes, you can have multiple DKIM keys by using different selectors. This is useful when you use multiple email services or want to rotate keys without downtime. Each key is identified by a unique selector in the DNS record.
How long should my DKIM key be?
DKIM keys should be at least 1024 bits, but 2048 bits is recommended for better security. Ark uses 2048-bit keys by default to ensure your emails are protected against current and future cryptographic attacks.
Related Terms
SPF
Sender Policy Framework (SPF) is an email authentication method that specifies which mail servers ar...
DMARC
DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication p...
Email Authentication
Email authentication is the process of verifying that an email was actually sent by the claimed send...
DNS Records
DNS records for email are entries in your domain's DNS that configure mail delivery (MX), sender aut...
Ready to improve your email deliverability?
Ark handles dkim and more automatically. Start sending in 5 minutes.