Custom domains with Fastmail

You might know a domain as what you type into your browser when you are trying to go to a website. Fastmail’s domain, for instance, is A domain name is part of a person or business's online identity. Owning a domain lets you choose where you direct all your online activity, including for your website or your email. 

Anyone can own and use a domain. A custom domain allows you to receive email at any address you like (such as, not just from Fastmail's many domains. By owning your domain, you can keep your email address the same, no matter what email provider you use.

In order to use custom domains with Fastmail, at least one admin of the account must be on a non-Basic subscription plan.

How do I buy a domain?

Domains can be purchased through a domain registrar. A domain registrar is a company that manages the purchase and ownership of domain names on the Internet. 

The option to register a domain through Fastmail is available to paid customers who have been with us for more than 7 days. If you buy your domain through Fastmail, it will be set up immediately to work with Fastmail, with no additional setup required. See our Registering a domain through Fastmail help page for more information.

If your Fastmail account is less than 7 days old, or if you want to buy a domain at a TLD we don’t offer, you will need to buy your domain from another registrar.

If you’re looking for a registrar, we recommend iwantmyname as a user-friendly option. There are numerous domain registrars to choose from, so it’s a matter of personal preference when deciding which one you’d like to use.

How do I use a custom domain?

If you purchase a domain from a domain registrar, you’ll need to make some changes to your DNS records so that you can send and receive mail from your domain. These changes are to be made through the control panel supplied by your registrar.

We have an interactive guide for setting up your domain. You can add your domain and begin using the guide in the Settings → Domains screen. We will check to see if your domain is registered, and guide you through the rest of the process.

We have more information about our domain setup wizard here.

For general information about the domain setup process and detailed guides, see below.

There are three different ways you can use Fastmail with your custom domain.

Nameservers hosted with Fastmail

  • This is the easiest, most commonly used option.
  • Host your custom domain with us: we will automatically configure your domain for email support, calendar syncing, contacts syncing and other security best practices (DKIM, SPF and more).
  • You will be able to manage your domain easily within your Fastmail settings. You can update your domain records if you want a website or want to use other services being hosted elsewhere.
  • We can detect many common configuration errors and will alert you to any issues.
  • It is not a good idea to change nameservers without preparation if you already have a website on your domain.
  • Step by step instructions on adding your domain to Fastmail with NS/MX

Nameservers hosted elsewhere, but MX records pointing to Fastmail

  • For users whose domain is already hosted elsewhere (and have no ability or desire to change nameserver host), but who would like to use Fastmail for mail hosting.
  • Changes must be made on the control panel supplied by your domain registrar. We provide you with the values you'll need to add to your DNS records.
  • Fastmail can detect some MX-related set up errors, and we'll notify you if there are issues.
  • Step by step instructions on adding your domain to Fastmail with MX-only

No NS/MX at Fastmail, but mail redirected to Fastmail

  • In rare cases, Fastmail isn't hosting the nameserver or the mail exchange records, but mail is still being redirected to Fastmail.
  • Use this option if you're using a third party filtering service to process mail before it is sent to us.
  • Fastmail's own spam filtering will be much less effective if you use this option.
  • We provide all the values you'll need to configure on your current MX server to ensure correct mail delivery. Fastmail is unable to detect misconfigurations in this case, as all the domain management is held elsewhere.
  • Step by step instructions on adding your domain to Fastmail with no NS/MX

Please note that only account administrators can manage custom domains on an account. If you’re not an administrator of your account but would like to use a custom domain, or are having issues with your domain, please be sure to contact your administrator.

Adding a subdomain as a domain

It's possible to add new users with an address using a subdomain if your account is already hosting mail for the primary domain. To do this, you will need to add as its own domain on the Settings → Domains screen.

If your domain's nameservers are already hosted with Fastmail, this setup will work automatically. If your domain is set up with MX records instead, then you will need to set Fastmail's MX records for * as well.

Once the subdomain has been added to the Settings → Domains screen, you can add users at this subdomain on the Settings → Users & Sharing screen.

Mirrored domains

With email, it's easy to have multiple domains that "mirror" each other. So you might have and, and you want any alias at to work at as well. To set this up:

  1. Go to your Settings → Users & Sharing → Aliases screen.
  2. Pick a "primary" domain (say, and create your domain alias using that domain.
  3. Next, create an alias using your alternate domain with the special * (star) value (e.g. * and set the target (the "deliver to" address) of the alias to *
    • After setting this up, any valid email address at will also work at
    • Note that this only works for email addresses; for websites, you have to explicitly create the website for each domain, or set up a redirect to the primary domain.

Internationalized Domain Names (IDN)

An internationalized domain name (or IDN) is a domain that contains non-ASCII characters. If your domain contains non-ASCII characters, you'll have to first convert the domain to Punycode before you can add it to your Fastmail account.

There are many websites that can convert non-ASCII script to Punycode for you, such as Enter your domain as the text, then convert it to Punycode. Once this has been done, you can copy and paste the Punycode as the domain name when adding the domain to your Fastmail account.

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