Cloudflare email routing + exchange online + custom domain

[DarkDeviL]

Mind if I ask, what exactly is your use case for using both Office 365 / Exchange Online, AND the Email Routing, at the same time?

@klieber

Is it possible to have cloudflare host the MX records for my custom domain (which are required for email routing to work) and yet still use Exchange Online for sending outbound email from that same custom domain? Including using DKIM?

Such kind of set up that you describe is technically possible, but will requires some sort of fiddling.

See for example:

Routing mail to own server with same name

Domains like e.g. example.com, example.net and example.org are standardized as example domains, such as for use in e.g. documentation, and, like in your case if you are not actually sharing a real domain name. This one is the major problem of your set up. While it isn’t technically impossible to do such things, they would require quite a bit of advanced rules (e.g. on Cloudflare’s side, in this situation). And, even if it was possible, those kind of advanced routing rules would make it easi…

Want to use both Godaddy and Cloudflare forwording email service

There is no way to use them both at the same time for the exact same (sub-)domain. If you are willing (and able) to switch GoDaddy to run on a sub-domain instead, such as e.g. @godaddy.example.com rather than @example.com, that could be a way.

@klieber

Near as I can tell, Exchange Online doesn’t like not being authoritative for the MX records, but I’m hoping I’m overlooking something.

Each service, when configured to accept messages for @example.com, will likely request the MX records for the example.com domain. Both of the above threads may provide a possible workaround for that.

The more stuff you stack on top of other stuff, the more fragile the overall setup will be, so I would normally advice against playing around with it like that.

According to your initial post, I see absolutely no reasons to stack the “Email Routing” on top of other stuff, such as e.g. Office 365 / Exchange Online.