If I have 2 services sending email using my domain name, can I set up DKIM for one but not the other?


I develop WordPress websites and frequently create contact forms that send email with a From address using the domain name of the website. Typically the business that the website is for is already using their own email service, which may or may not be configured with DKIM.

Whether or not DKIM is already set up for the existing email service (let’s say it’s Office365) using the domain, I want to know whether I can negatively affect the deliverability of the email from the existing email service if I add a DKIM key for an additional mail server (used by the WordPress website) to send email, with a From address containing the domain name.

ie assuming I configure a DKIM record correctly for the WordPress website to send email using the mail server of the hosting service, can the Office365 email deliverability be affected?

Note: I do see it’s possible to have 2 DKIM records, for multiple services, but they must have different selectors: https://stackoverflow.com/questions/32649006/can-i-have-multiple-dkim-txt-records-in-single-domain