I am curious if anyone has come across a similar issue? My DNS is currently setup for my Google Workspace for email routing, which is working great. I’m trying to integrate Mailgun for our auth provider, and adding the MX info for those is causing the auth emails to not be delivered. Has anyone had a situation like that where they had multiple different MX keys for different products under the same DNS? For example:
You cannot mix MX from different providers on the same domain without rendering your incoming email completely useless. If you need Mailgun to send from the same domain as Google and you need to receive email at Google, you will need to forfeit the use of the Mailgun MX. You may be able to create user specific transport routes in Google that can get certain addresses sent to Mailgun, but I don’t know of a good reason to expend the effort.
I prefer to deploy Mailgun on a subdomain. It alleviates the MX conflict making things considerably easier to manage. As long as you use relaxed DKIM and SPF, you can still pass DMARC with the organizational domain in the RFC 5322 From field.
