DKIM, Gmail and emails sent from both code and outlook

Question

I have a business email address: [email protected].

I use this to send order confirmation emails thru a variety of different systems, one of which is a .net web app that sends emails thru AWS SES. There are 2 other systems that send out emails automatically using the same email address via smtp.gmail.com.

I also use that email address locally with Outlook to manually send some emails, and allow people to reply directly to the order notification emails.

I notice now that my AWS SES emails come into gmail with a little tag - 'sent via amazonses'. I more or less understand why that is there and how to get rid of it by setting up the DKIM stuff.

What I don't understand is how adding a DKIM record thru AWS effects my local setup with outlook and smtp.gmail.com. Do I create multiple DKIM records? one thru AWS for SES, and one thru GMAIL?

Answer 1

DKIM keys have a notion of 'selector'. A selector is an identifier for the particular DKIM key for the domain used to sign a message. This allows multiple DKIM keys to be defined for a domain, and hence allows multiple independent senders to sign messages using DKIM.

The corresponding DKIM key record in DNS can be found at

<selector>._domainkey.<domain>

Google (Gmail) typically uses the selector 'google'. So for your example above, the DKIM key record for Gmail would be published at

google._domainkey.mybusiness.com

Other signers would use different selectors, allowing you to publish multiple, non-conflicting keys.