11 May 2016

How to add those long 2048 bit DKIM keys to a TXT field that only supports 255 characters

Adding DKIM email authentication to your Google Apps emails is a great way to improve security and to verify that each email you sent is actually sent by you, and not from some spam email guys that no ones wants to talk about.

Anyway, Google Apps have updated their DKIM to be 2048 bit long in order to improve security. But, not many DNS services support long keys yet. Having to enter the public DKIM key to the TXT record of your DNS, which doesn't fit because the TXT field has a 255 characters limit, and you can see how this can be a problem.

Looking for a solution for my own emails, I found this procedure that allowed me to use 2048 bit DKIM keys without the need to move to another DNS provider completely.

Here is the step-by-step video tutorial on how to solve this:

The steps explained in this video tutorial are as follow (but frankly, you would be much better off just following the video itself):

  1. Generate the long 2048 bit DKIM in Google Apps
  2. Find a DNS service that support long TXT values (you will still be able to keep your previous DNS. We need this for the DKIM only)
  3. Create a subdomain on the new DNS and add your DKIM key to the TXT field
  4. Now on your previous DNS, add a CNAME instead of TXT record that will lead to the new DNS service, using the same DKIM hostname (ex. google._domainkey)
  5. Test that your implementation is working and active using DKIMCore or DKIM Key Checker (as these web apps support 2048 bit DKIM keys)
  6. If everything checks up correctly, active the DKIM Email Authentication on Google Apps

I hope you'll find this tutorial useful and finally solve your DKIM issues.

The DKIM validators used in the video are:
DKIMCore - http://dkimcore.org/tools/keycheck.html 
DKIM Key Checker - https://protodave.com/tools/dkim-key-checker/

Thanks goes to Steve Atkins for creating DKIMCore and Dave Johnson (protodave) for DKIM Key Checker.

Thanks goes to David Ensinger for his post about NameCheap DKIM:

Big thanks also goes to Jenny Velle from Google Apps for her amazing support and dedication, that helped a lot in making this solution possible.