A question we get a lot when someone sets up newsletter sending on their own domain: "Why do I have to use a subdomain like send.mydomain.com? Why can't I just send from mydomain.com?"
It's a fair question, and the answer is one of those "it's not us, it's how DNS works" things. Here's the plain-English version.
First, the reassuring part
Your subscribers do see your main domain. You can set your newsletter's from address to newsletter@mydomain.com, hello@mydomain.com, or whatever you like at your main domain – that's what shows up in the inbox.
The subdomain is only the technical sending domain: the plumbing that actually hands your email to Mailgun, the email infrastructure provider we use, and proves it's really from you. Your readers never see it. So this isn't about what your emails look like – it's purely about the records behind the scenes.
The actual reason: your root domain is already busy
Modern email sending uses a CNAME record. A CNAME is a DNS record that says "for this name, go look over there instead" – in our case, your subdomain points at email.magicpages.co, which carries all the authentication (SPF, DKIM) for you.
Here's the catch, and it's a hard rule of DNS: a name that has a CNAME can't have any other records at the same time. It's all-or-nothing.
Your root domain (mydomain.com, also called the apex) can never be all-or-nothing, because it already must hold other essential records – the ones that tell the internet which name servers run your DNS, for a start. If you tried to turn your root domain into a CNAME, you'd wipe those out and take your whole domain offline.
A subdomain (send.mydomain.com) has no such baggage. It's a fresh name you can point wherever you like – so it's free to be the CNAME that sending needs.
It's the same reason your website uses a subdomain or an A record
If you've ever set up a custom domain for a website, you may have hit this exact limitation from the other direction: you can't point your root domain at a host with a CNAME either, which is why site setups use www or require a special setup with Cloudflare.
We wrote about that here:
Jannis Fedoruk-Betschki
Same rule, different feature – the apex just can't be a CNAME.
If you're setting this up, the sending domain guide walks you through it.
