Posteo Custom Domain: Why You Can't, and How to Use Proton or Fastmail Instead

Posteo is one of my favourite privacy providers, and at €1 a month it’s hard to beat. But if you want an address at your own domain, such as you@yourname.com, Posteo can’t do it. Here’s why, the one workaround, and step by step instructions for the two providers I’d pick instead: Proton Mail and Fastmail.

Why Posteo Doesn’t Support Custom Domains

This is a deliberate choice, not a missing feature. Posteo lets you sign up without giving your name, and it keeps as little data about you as it can. Domain registration involves identity data, and supporting custom domains would mean storing and associating personal information with accounts. That goes against how Posteo works, so it simply doesn’t offer it.

I respect that. It’s also the one thing that stops Posteo being my main inbox, as I explain in my Posteo review. Your own domain means you can change provider whenever you like and keep your address, which I cover in why using your own email domain makes sense.

What Posteo Does Offer

• A choice of Posteo domains: your main address can use one of Posteo’s own domains, not only posteo.de.
• Aliases: you can add extra addresses on around 50 Posteo domains, which is handy for keeping sign ups separate.
• Receiving from your domain: you can forward mail for your own domain to Posteo using a separate forwarding service. More on that below.

The Workaround: Forward Your Domain to Posteo

If you only need to receive mail at your domain, you can forward it to your Posteo inbox. If your domain’s DNS is on Cloudflare, Cloudflare Email Routing does this for free:

1. In Cloudflare, open your domain and go to Email > Email Routing.
2. Click Get started and let Cloudflare add its MX and SPF records.
3. Add your Posteo address as a destination and click the link in the email Cloudflare sends you.
4. Create a rule, such as you@yourdomain.com to your Posteo address, or a catch all.

The Best Posteo Alternatives for Your Own Domain

Proton is the pick if encryption matters most. Fastmail is the pick if you want the smoothest everyday email and standard apps. I compare them in detail in Proton Mail vs Fastmail. If you want something closest to Posteo, read my mailbox.org review.

How to Set Up Your Own Domain on Proton Mail

1. Sign in to Proton Mail on the web and open Settings.
2. Go to Domain names and click Add domain.
3. Type your domain and click Next.

Proton shows a TXT record that starts with protonmail-verification=. Add it to your DNS:

Go back to Proton and click Verify. If it fails, wait a few minutes and try again.

Proton asks you to create addresses, such as you@yourdomain.com, before you move your mail. Do this now, so mail has somewhere to land when you switch the MX records.

Always copy the values from your own Proton screen, in case they change. Proton suggests a TTL of 300 seconds while you set up.

Back in Domain names, Proton checks each record and shows a green tick when it’s right. It can take from a few minutes to a few hours. Then send yourself a test email from another account.

How to Set Up Your Own Domain on Fastmail

1. Sign in to Fastmail and open Settings.
2. Go to Domains and click Add or buy domain.
3. Choose Use a domain you already own and type your domain.

Fastmail asks how you want to handle DNS. The simplest choice, and the one I show here, is to keep your DNS where it is and add Fastmail’s records yourself.

Swap yourdomain.com for your own domain in the three DKIM values.

Go back to Settings > Domains. Fastmail shows a green tick next to each record once it can see it.

Go to Settings > Mail preferences > Compose and pick your new address as the default From address. Then send a test email to a friend or a Gmail account and reply to it.

Moving From Posteo

If you’re leaving Posteo for your own domain, there’s no rush to close your Posteo account. Keep it for a few months, tell your contacts your new address, and add a forwarding rule in Posteo’s settings so nothing gets missed. Both Proton and Fastmail can import your old mail.

Frequently Asked Questions

Does Posteo support custom domains?

No. Posteo only offers addresses on its own domains. It says supporting your own domain would mean storing personal data linked to your account, which goes against its privacy model.

Will Posteo add custom domains in the future?

I wouldn’t count on it. It’s a deliberate choice rather than something on a to do list.

Can I send email from my own domain through Posteo?

Not properly. You can forward incoming mail for your domain to Posteo, but replies go out from your Posteo address.

What is the cheapest privacy email with a custom domain?

Proton Mail Plus and mailbox.org are among the cheapest. Check each provider’s current prices, as they change often.

Proton or Fastmail for my own domain?

Choose Proton if end to end encryption matters most. Choose Fastmail if you want standard apps, IMAP and the smoothest everyday experience.

How long does it take for DNS changes to work?

Usually a few minutes, sometimes a few hours. Both Proton and Fastmail show green ticks when they can see your records.

Note: this article contains referral links for Proton Mail and Fastmail. Sources: Posteo: domains for alias addresses; Proton: how to use a custom domain; Fastmail: set up your domain. Checked 4 November 2026.