Setting up your domain: MX only

This option is good for users who have a website at their domain, but who would like to use Fastmail to handle their mail.

Final setup must be done on the control panel supplied by your domain registrar. We can provide you with the values you'll need to add to your DNS records.

There are three general steps involved:

  1. Add your domain
  2. Domain registration set up
  3. Add email addresses at your domain

Additional information:

We also have guides for setting up your domain's MX records with some common domain registrars:

1. Add your domain

We have a setup guide to help you get your domain working as quickly and easily as possible.

Go to the Settings → Domains screen. Then, add your domain(s) (e.g.

Click the Add or buy domain button, then choose the Use a domain you already own option. This will bring up the domain wizard. Type your domain into the box. We will detect whether your domain has been registered or not. It's important that the domain has already been registered by you at a domain registrar; otherwise you won't be able to make the necessary changes.

Follow the on-screen prompts to continue adding your email addresses and setting up your domain. At the end, we will generate the instructions that match your situation. The general instructions for editing your MX records are below.

Please note: If you are on a legacy plan, the domain setup wizard can only set up email addresses, not users. You will need to add users manually in order to create additional user accounts at your custom domain.

2. Domain registration set up

Note: Updating your DNS is a big change: we recommend updating it at a time you don't expect much mail.

Set your MX records to:

  • (first, priority = 10)
  • (second, priority = 20)

If your DNS provider asks for a host name, this can be entered as @.

These should be the only two MX records listed for your domain

Some DNS providers require that you put a . on the end of the MX server names (e.g. rather than Try the version without a . first, and if the DNS provider adds anything, try adding the ..

In addition to MX records, you will need to add SPF, DKIM, and DMARC entries to make sure emails you send don't get marked as spam. You will need to add the following entries (be sure to replace {} with your actual domain):

Type Selector Value
TXT (leave blank) v=spf1 ?all
CNAME fm1._domainkey fm1.{}
CNAME fm2._domainkey fm2.{}
CNAME fm3._domainkey fm3.{}
TXT _dmarc.{} v=DMARC1; p=none;

If your DNS provider requires a host name for the TXT record, this can be entered as @.

Once we detect that your MX records are set up correctly, go to Settings → Domains, click Edit on your domain and we'll show you if everything is set up correctly.


See our DNS page for more information.

Combining SPF records

Please note that having more than one TXT record starting with v=spf1 will cause an issue with SPF detection.

If you need to add SPF for more than one service, you can combine multiple SPF records into one TXT record. To do so, add the SPF records between the v=spf1 and all strings. The TXT record should look something like this:

v=spf1 ?all

You can include up to 10 SPF records.

Setting MX records for subdomains

If you also want email for subdomains to come to us, you need to set the MX records for * to the above values as well. If you intend to send mail from subdomain addresses, then you'll also need to add DKIM for your subdomain as well:

Type Selector Value
CNAME fm1._domainkey.subdomain fm1.{}
CNAME fm2._domainkey.subdomain fm2.{}
CNAME fm3._domainkey.subdomain fm3.{}

Note for Cloudflare users

If you use Cloudflare, you will see an orange cloud icon when editing your CNAME entries. This orange cloud means that your DNS entries are being routed through Cloudflare's proxy. You will need to make sure these icons are toggled to gray so that your DNS can be correctly detected.

3. Add email addresses at your domain

Email addresses for your domain are added during the domain setup process. If you need to add additional email addresses at a later date, these can be added in the Settings → My email addresses screen. You may also choose to add a catch-all address if one was not already set up with the domain, so that any mail addressed to your domain comes to you, no matter what address is used.

You can customize other settings too, such as your signature.

If you'd like to set up one of your custom domain addresses as your account's default address:

  1. Go to the Settings → My email addresses screen.
  2. Select your address in the Set default dropdown list.

Double checking the DNS changes

How long until it's working?

Depending on the TTL values for your previous DNS settings (if any), it may take up to a day for the changes to propagate across the internet. Normally it's a lot faster: just a matter of minutes. Once your domain is set up correctly and active on Fastmail, messages sent to the addresses you added should now arrive in your Inbox.

How do I know it's right?

Your Settings → Domains screen shows a green tick when it has detected that your DNS entries are complete and correct. Any lingering issues are marked with a red exclamation point and a recommendation on how to resolve this issue.


Optional domain setup

System email addresses

The email standard requires that the email address be a valid email address. Because of this, even if you don't set up this address, we will deliver any email sent to that address to the owner of the domain.

It's also best practice to support By default, if you don't set up your own address for, we'll automatically direct all email sent to to our abuse handling system.

Subdomain addressing and mail routing

On the Settings → Domains screen, you can control subdomain addressing and mail routing. Click Edit next to your domain. In the Routing section, click on Manage


The Subdomain addressing options section lets you control how Fastmail handles subdomain addressing for your domain. There are three options:

Option 1: Accept mail to and deliver it to

With this option, subdomain addresses are handled like regular Fastmail domains, following plus addressing rules. This is the default option, and we recommend keeping this option selected for ultimate flexibility.

Option 2: Accept mail to and deliver it to

With this option, the subdomain portion is ignored, and mail is delivered to your inbox.

Option 3: Reject mail to 

With this option, mail to subdomains is disabled for your domain. This can mean two things:

    • If the DNS for a subdomain points to us, then sending to that subdomain will be rejected and bounced.
    • If the DNS for a subdomain points to other servers, then sending to that subdomain will direct email to the appropriate servers.

The Mail: Routing section lets you choose how mail to this domain is handled.

  • Internal routing: Fastmail is handling all of your mail activities. This provides proper loop detection preventing inadvertent mail loops (via addresses or forwarding) that could cause spam or over-quota usage. While in this state, the DNS records for the domain are only checked every day.
  • External routing: Some or all of your email activities are hosted elsewhere; whether this is the mail itself or things like mailing lists. No loop detection is possible. While in this state, the DNS records for the domain are checked every hour to see if they have changed.
Was this article helpful?
76 out of 103 found this helpful