A Sender Policy Framework (SPF) record indicates mail servers that are authorized to send mail for a domain. Email recipient servers perform a check with DNS to see if the mail came from an authorized server. If not, then the email is most likely SPAM. SPF DNS records lets the recipient server perform this verification.
A DomainKeys Identified Mail (DKIM) record adds a digital signature to emails your organization sends. Email recipient servers perform a check with DNS for the to see if the DomainKey matches the sender. If so, then the email is considered unmodified and from a legitimate sender. DKIM DNS record lets the recipient server perform this verification.
Configure Google Apps SPF
If you use Google Apps for email, you’ll need access to your DNS provider to add an SPF record. In most cases, you simply login and create a new TXT record with the value of:
v=spf1 include:_spf.google.com ~all
Google provides detailed instructions on how this is done. Be sure to save your changes.
Configure DKIM for Google Apps
You’ll need access to your Google Apps control panel and your DNS records to set DKIM. This is a three step process:
1. Create the DKIM key
a. Login to your Google Apps Control Panel (e.g., http://www.google.com/a/cpanel/yourdomain.com)
b. Navigate to the Gmail App Control Panel
c. Scroll down to “Authenticate email” and click on “Set up email authentication (DKIM)”.
d. Your domain name should be displayed. Click on “Generate new record”. Leave the default selector prefix as “google”. Click “Generate”.
e. Leave this browser window open, and then create a new tab or browser window.
2. Create the DKIM DNS record
a. Login to your DNS provider.
b. Create a new TXT record. The name of the TXT record should be:
google._domainkey
This creates a domain that, fully resolved, looks like: google._domainkey.yourdomain.com.
c. The value for the DNS record will be a very long string of characters, something like:
v=DKIM1; k=rsa; t=y; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCG5in7gQIDAQAB
The actual length of the string will be much longer than that above. I find it simplest to copy-and-paste the information from the Control Panel page displaying the information. Save the DNS record.
3. Start Authenticating
a. Wait 24-hours for your changes to propagate, and for Google’s servers to detect the changes.
b. Login to your Google Apps Control Panel (e.g., http://www.google.com/a/cpanel/yourdomain.com)
c. Go to the “Advanced tools” tab, then scroll down to “Authenticate email” and click on “Set up email authentication (DKIM)”.
d. Click “Start authentication”.
As always, check Google’s detailed instructions if your setup is more complex.
Verify that SPF & DKIM are configured
Send an email from your Gmail account to check–auth@verifier.port25.com after you’ve completed the Google Apps SPF and DKIM setup. You’ll receive an email response in a few minutes. If everything is properly configured, you’ll receive a “PASS” for both the Google Apps SPF and DKIM settings. This means your email is now securely being delivered and can be verified as such.