Email Routing: MX priorities

Out of curiosity, why does Cloudflare recommend DNS MX priorities that are odd looking e.g. 5, 18, 98 or 11, 12, 95? Hip factor or is there more to it?

Anything wrong with 1, 2, 3 or 10, 20, 30? Or even the same priority and let the sender pick an order?

I believe it might be due to the:

My guess it’s how they “verify” that your domain is properly set up for email forwarding.


Similar to “Ninja” name server records? I agree, but don’t see the point. They could just put an On/Off switch on the dashboard to turn CF MX records on or off. No need to verify anything then, as it would all be under CF control. Except for CNAME setups.

They shouldn’t care about the numbers but rather what the actual order is. I’ve set mine to 10, 20, 30 and Cloudflare seems happy.

Priorities of 1,2,3 make it extremely difficult to reorder on the fly and with 64k+ possible values makes life more difficult than it needs to be.

Values of 10, 20, 30 lead PHBs to think that adding an intermediary record with a value of 25 is sloppy and other records should be reordered to match a pattern that matters not at all.

When the average user of DNS forwarding wants to move from this system to something like Office 365 if the numbers were the same as what Microsoft told them to change their Mx records to the odds they’d be confused enough to open a support ticket would increase substantially.

Priority doesn’t really matter ATM, as far as I can tell all the hosts resolve to the same unicast IP address. And even if it did change multiple IPs… Cloudflare’s just an MTA relay so it still doesn’t really matter.

So why not go the Office 365 route, one record pointing to, set priority 0, and let Cloudflare manage everything else?

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Not my product or company, but I would set multiples to give myself more flexibility in the future for experimentation (it’s a free service… you are the product/experiment).

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Cloudflare’s Email Routing MX priority are random, we don’t rely on MX ordering.

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Safe to set them to anything in DNS and Cloudflare won’t think that MX is not configured correctly?

We don’t validate right now but we might in the future. I recommend to leave what was setup automatically, MX priorities won’t impact your service.

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What about the SPF record? I need to merge the Cloudflare one with other includes for my domains. I assume that should be OK.

i’ve merged spf. works fine.

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