To ensure that your DKIM (DomainKeys Identified Mail) or DK (DomainKeys) signature is valid, you need to correctly configure your DKIM settings on your mail server and verify that the signatures are being correctly applied and recognized by the recipient servers. Here’s how you can do it:
Step 1: Generate DKIM Keys
Generate a DKIM Key Pair: Most mail servers or hosting providers offer tools to generate a DKIM key pair (public and private keys). If you’re managing your own server, you can use tools like openssl to generate these keys.
Public Key: This key will be published in your domain's DNS as a TXT record.
Private Key: This key will be used by your mail server to sign outgoing emails.
Step 2: Publish the DKIM Public Key in DNS
Create a TXT Record: In your DNS management interface, create a new TXT record.
Name/Host: The name should be in the format selector._domainkey.yourdomain.com, where selector is a name you choose (like default or mail).
Value/Content: The value should contain the public key, in this format:
v=DKIM1; k=rsa; p=your_public_key_here
v=DKIM1: Specifies the DKIM version.
k=rsa: Specifies the key type (RSA).
p=your_public_key_here: Replace with the actual public key.
Step 3: Configure Your Mail Server to Use DKIM
Enable DKIM Signing: Configure your mail server or email service provider to sign outgoing emails with the DKIM private key.
Set the Selector: Ensure that the selector name in your mail server configuration matches the selector used in your DNS record.
Test the Setup: Send a test email to ensure that the DKIM signature is being applied.
Step 4: Send a Test Email
Send to a Testing Service: Use a service like Mail-tester, MXToolbox DKIM Lookup, or Gmail to verify your DKIM signature.
Analyze Results: Check the headers of the received email to see if the DKIM signature is valid.
In Gmail, open the email, click the three dots next to the reply button, and select "Show original."
Look for the DKIM-Signature header and a line that says dkim=pass. If it says pass, the signature is valid.
Step 5: Verify DKIM Configuration
Check with MXToolbox: Use the MXToolbox DKIM tool to look up your DKIM record and verify that it's properly configured and visible.
Step 6: Check Email Headers
Inspect Headers: Look at the headers of a sent email to ensure the DKIM signature is present and correct.
DKIM-Signature Header: The header should look something like this:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yourdomain.com; s=selector;
h=from:to:subject:date; bh=hash_value;
b=signature_value;
Validation: The receiving server should verify this signature against the public key in your DNS record. If the signature is valid, the email should pass DKIM validation.
Step 7: Monitor DKIM Performance
Regularly Review DKIM Reports: If you have set up DMARC, you'll receive reports that include DKIM validation results, helping you monitor the effectiveness of your DKIM setup.
Troubleshooting DKIM Issues
DNS Propagation: If you’ve just set up DKIM, give it time for DNS changes to propagate.
Mismatched Selectors: Ensure the selector in your mail server matches the one in your DNS record.
Correct Formatting: Double-check that there are no line breaks or spaces in the middle of your p= value (public key) in the DNS record.
By following these steps and regularly testing, you can ensure that your DKIM or DK signature is valid and properly securing your emails.
how to get a DKIM Public Key in DNS
To get a DKIM public key in your DNS, you need to generate the DKIM key pair (public and private keys) and then publish the public key as a DNS TXT record. Here's how you can do it:
Step 1: Generate a DKIM Key Pair
Using Your Email Service Provider:
Email Service Provider: If you're using an email service provider (e.g., G Suite, Microsoft 365, cPanel), they typically offer a tool to generate DKIM keys. Follow their instructions to generate the keys.
cPanel Example:
Log in to cPanel.
Navigate to Email > Email Deliverability.
Locate your domain and click "Manage."
Enable DKIM and cPanel will generate the key pair for you.
Manually Generating DKIM Keys:
Linux Command Line: If you're managing your own server, you can generate the key pair using openssl:
Run the following command to generate a 2048-bit private key:
openssl genrsa -out private.key 2048
Extract the public key from the private key:
openssl rsa -in private.key -pubout -out public.key
Step 2: Prepare the DKIM Public Key for DNS
Format the Public Key: The public key needs to be in the correct format for DNS:
Open the public.key file and copy the key content.
Remove the -----BEGIN PUBLIC KEY----- and -----END PUBLIC KEY----- lines, leaving just the base64-encoded key.
Remove any line breaks, so the key is a single continuous string.
Step 3: Add the DKIM Public Key to Your DNS
1.Access Your DNS Management Interface:
Log in to your DNS hosting provider’s control panel (e.g., GoDaddy, Cloudflare, Namecheap, etc.).
2.Create a New TXT Record:
Type: Select TXT as the record type.
Name/Host: Enter the selector name, followed by .domainkey.yourdomain.com.
Example: If your selector is default, the host name would be default.domainkey.yourdomain.com.
Value/Content: Enter the DKIM public key in the following format:
v=DKIM1; k=rsa; p=your_public_key_here
v=DKIM1: Indicates the DKIM version.
k=rsa: Specifies the key type (RSA).
p=your_public_key_here: Replace this with the actual public key from the previous step.
3. Save the DNS Record:
Save the TXT record in your DNS management interface.
Step 4: Verify the DKIM Record
Use Online Tools: After DNS propagation (which can take up to 48 hours), verify the DKIM record using tools like:
MXToolbox DKIM Lookup
DKIMCore
Check via Command Line: You can also use command-line tools like dig to check the DKIM record:
dig TXT default._domainkey.yourdomain.com
Example of a DNS TXT Record
If your selector is default and your domain is example.com, the DNS record would look like this:
Type: TXT
Name/Host: default._domainkey.example.com
Value/Content:
v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7gW9Jt...
Step 5: Configure Your Mail Server
Match the Selector: Ensure that the selector used in your mail server matches the one used in your DNS record.
Enable DKIM Signing: Configure your mail server to sign outgoing emails with the DKIM private key.
Conclusion
By following these steps, you can successfully publish your DKIM public key in DNS. This will allow receiving mail servers to verify the DKIM signature on your outgoing emails, helping to ensure that they are properly authenticated and less likely to be marked as spam.
