# How to find your DKIM selector and check your key

Source: https://www.tryletterhead.com/blog/find-dkim-selector.html

A real result from the DKIM checker, run on tryletterhead.com.

Your DKIM selector is the label your email platform uses to tell receivers where to find your public key. To find it, open the source of any email you sent, find the DKIM-Signature header and read the s= value. The key itself lives at selector._domainkey.yourdomain.com.

The quicker route: paste the full source of an email you sent into the free [DKIM checker](../tools/dkim-checker.html), and it reads the selector from the signature for you.

## Where is the DKIM selector in an email header

Every signed message carries a header like this one:

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=yourdomain.com; s=s1; h=from:to:subject:date;
bh=...; b=...

Two tags matter here:

- s= is the selector, here s1.

- d= is the signing domain. For your mail to pass DMARC through DKIM, it should be your domain, not your email platform's.

So this message's key lives at s1._domainkey.yourdomain.com.

## How do you find your DKIM selector in Gmail, Outlook and Apple Mail

Use a newsletter you sent that landed in your own inbox, or ask a colleague to forward the original.

- **Gmail on the web:** open the message, click the three-dot menu next to Reply, and choose **Show original**. Search the page for DKIM-Signature.

- **Outlook on the web:** open the message, choose **More actions**, then **View** and **View message source**.

- **Apple Mail:** open the message, then choose **View**, **Message**, **Raw Source**.

## What does a DKIM record look like

Part
Example
What it is

Host
s1._domainkey.yourdomain.com
The selector, then _domainkey, then your domain.

Type
TXT (or CNAME)
Many platforms ask for a CNAME that points at a key they host, so they can rotate it.

Value
v=DKIM1; k=rsa; p=MIIBIjANBgkq...
p= holds the public key, a long string of letters and numbers.

Key length matters. Yahoo's sender requirements ask for keys of at least 1024 bits and recommend 2048.

## What are the common default selectors

Google Workspace uses google unless you changed it. Microsoft 365 uses selector1 and selector2. Most newsletter platforms list their selector on the page where they give you DNS records to add, so check there before you go hunting.

_Free tool · DKIM checker_

Find your DKIM selector and check your key.

Type your sending domain, or paste an email you sent and we read the selector from its signature. No signup.
[Check your DKIM](../tools/dkim-checker.html)

## Why does DKIM fail when a key is published

- **The platform signs with its own domain.** If d= shows your platform's domain, DKIM passes but doesn't line up with yours, so it doesn't help DMARC. Set up DKIM on your own domain in the platform's settings.

- **The key in DNS is out of date.** After a key rotation, the old TXT record no longer matches what the platform signs with.

- **The record got cut off.** Long keys sometimes get truncated or split badly by a DNS host. Compare the published value with what the platform gave you.

- **The message changed on the way.** Mailing lists that add a footer or rewrite the subject can break the signature.

New to DKIM? Start with [what is DKIM](../blog/what-is-dkim.html). DKIM is one of the two checks DMARC relies on, so read [what is DMARC](../blog/what-is-dmarc.html) next.

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#deliverability #dkim #how-to

_Keep reading_

## More on this topic.
[What Is DKIM, and Where Is Your Selector?
DKIM signs every email you send so receivers can trust it came from you. How it works, how to find your selector in two minutes, and what changes when you switch platforms.
Read the post](../blog/what-is-dkim.html)[How to Measure Your Newsletter's Success: Key Metrics
Discover the key metrics to measure your newsletter's success and optimize your strategy for better engagement and results. Learn how to track essential metrics and improve your newsletter…
Read the post](../blog/how-to-measure-your-newsletters-success-key-metrics.html)[How To Find Sponsors For Your Email Newsletter
Unlock Profit Potential! Start an Email Newsletter Business today and learn from successful examples and monetize your newsletters. Get inspired to launch your own venture. Read more.
Read the post](../blog/how-to-find-sponsors-for-your-email-newsletter.html)

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