DomainKeys Identified Mail (DKIM) is one of the three main email authentication standards that mailbox providers and spam filters use to decide whether to trust an email.
When you don’t have a valid record, or if your keys “break”, your outreach campaign, whether you’re doing PR outreach, link building, or sales, won’t see great results.
In this blog, I’ll discuss what DKIM is, why it’s important, and how to make sure this isn’t an issue for any email campaign.
Let’s dive in!
What is DomainKeys Identified Mail (DKIM)?
A DKIM record is a unique DNS TXT record that your domain publishes so receiving mail servers can verify your emails. It works by adding a digital signature to each outgoing message, and the receiving server checks this signature against the public key in your DNS record.
This ensures that your email hasn’t been altered in transit and confirms it really came from your domain. Without a valid DKIM, your messages risk being flagged as spam or rejected outright.
Having a valid DKIM record is critical for email deliverability. Mail providers like Google and Microsoft use it as one of the main checks to decide whether your message is trustworthy.
When DKIM is set up correctly, your emails are more likely to land in the inbox instead of the spam folder. But if your DKIM is missing or broken, it can raise red flags for spam filters and cause your outreach campaigns to fail before they even reach your prospects.
DKIM also isn’t the only record you need. It works alongside SPF and DMARC, which are the other two main email authentication records. In short, SPF tells mail providers which servers are allowed to send on your domain’s behalf. DMARC gives instructions on what to do if a message fails authentication. DKIM’s role is to prove the message wasn’t changed along the way.
When all three are set up, they give your domain more credibility and make it harder for spam filters to doubt you.
Common DKIM Issues That Can Hurt Deliverability
Even small mistakes with DKIM can have a big impact. A missing record, an expired key, or even a typo in your DNS can cause verification to fail.
Some email providers, like Outlook, rotate keys, so if you’re not keeping both selectors active, one of your signatures might break. When that happens, spam filters see your emails as less trustworthy, and your outreach efforts take the hit.
When DKIM fails, you usually won’t get a big red warning telling you what went wrong. Instead, you’ll see the effects in your deliverability. Your emails might start landing in spam, open rates will drop, or, in some cases, messages won’t reach the inbox at all.
The tough part is that this can look just like a copy issue or low domain reputation—so if you don’t check your records, you may not even realize DKIM is hurting you.
The good news is you don’t need to guess whether your DKIM is working. There are free tools online that make it easy to check. Sites like MXToolbox, EasyDMARC, and Google’s own admin tools will tell you if your record is set up correctly and if the signature is passing.
All you have to do is enter your domain, and the tool will scan your DNS records and show you any errors. Running these checks regularly helps you catch problems before they tank your deliverability.
We run DKIM audits every week as part of our deliverability process. Even small DNS changes or email provider updates can break a record without warning, so checking regularly helps us catch issues early.
We recommend you do the same—make DKIM testing part of your routine so problems don’t pile up and drag down your campaigns.
How to Set Up a DKIM Record
Setting up a DKIM record starts with your Email Service Provider (ESP). Each platform has its own way of generating and publishing the DNS TXT record, so the first step is always to follow the instructions from your ESP directly.
In most cases, you will generate a key inside their dashboard, publish the TXT record in your DNS, and then verify that everything is passing once the changes propagate. It sounds technical, but the process is usually straightforward if you follow the provider’s guide step by step.
To simplify setup, we’ve compiled a full reference of platforms with links to their detailed walkthroughs:
Major Email Service Providers / Infrastructure
- Google Workspace (Gmail)
- Microsoft 365 (Outlook)
- Amazon SES
- Twilio SendGrid
- Mailgun
- Postmark
- SparkPost
- SMTP2GO
- Elastic Email
- Mailjet
- Brevo (Sendinblue)
Marketing Email Service Providers
- Mailchimp (Marketing)
- Klaviyo
- Campaign Monitor
- HubSpot
- ActiveCampaign
- Constant Contact
- AWeber
- MailerLite
- GetResponse
- Zoho Campaigns
- Omnisend
- Moosend
- Drip
- ConvertKit
Transactional Email Service Providers
Enterprise Marketing Clouds
E-commerce & Site Platforms
Follow official instructions on how to generate and publish your DKIM record.
We recommend using those guides directly. Each one will walk you through the exact steps and help you avoid common mistakes like typos or missing selectors.
By following your ESP’s setup process, you will make sure your record is valid from the start and that your outreach has the best chance of reaching the inbox.
The Bottom Line on DKIM
Making sure your DKIM records are rotating and validated is important for any email outreach campaign. It’s one of the easiest ways to build trust with mail providers and keep your messages out of the spam folder.
When you pair DKIM with SPF and DMARC, you create a solid foundation that tells inboxes you’re a legitimate sender.
