Google Domains’ domains moved to Squarespace: if your domain was there, its DNS is now edited at Squarespace Domains.

Before you start

Access to the panel where the domain’s DNS is edited. Usually it is at Squarespace Domains (formerly Google Domains), but if the domain uses another company’s DNS servers (nameservers), the zone is there and that is where you work.
If the domain already receives email somewhere else (a hosting mailbox, Google Workspace, Microsoft 365), changing the MX makes new email come through mxproxy. Old messages stay where they are.
An mxproxy account. Create yours for free, no card.

1. Add the domain to mxproxy

Create the account (or sign in) and, under Domains, add your domain, for example yourdomain.com.
Open the domain: the page shows the DNS records to create. Keep that tab open; you will copy the values from it.

The DKIM key and the code of the _mxproxy TXT are unique to each domain: copy them from the dashboard, not from this guide.

2. Open Squarespace Domains’ DNS zone

In Squarespace’s domains dashboard, click the domain.
Open DNS › DNS Settings.
Scroll to Custom records and use Add record for each record. To edit a record, Squarespace asks for your password (or second factor) again.

How to fill in the name (host) at Squarespace Domains (formerly Google Domains)

Use @ on the MX. On the others, only the beginning (_mxproxy, _dmarc, the selector with ._domainkey), without the domain: Squarespace adds it. The Priority field takes 0 to 255.

3. Create the MX, SPF, DKIM and verification records

Create these records in the domain’s zone. The first two are the same for everyone; the last two have values of their own, which you copy from the mxproxy dashboard.

DNS records for mxproxy to receive and send for your domain
Type	Name (host)	Value	Priority
MX	`@`	`mx.mxproxy.dev`	`10`
TXT	`@`	`v=spf1 include:spf.mxproxy.dev ~all`	—
TXT	`mx202610._domainkey` the selector the dashboard shows	`v=DKIM1; k=rsa; p=…` copy from the mxproxy dashboard	—
TXT	`_mxproxy`	`mxproxy-verify=…` copy from the mxproxy dashboard	—

One SPF only. If the domain already has a TXT starting with v=spf1 (from a host, Google, an online store), do not create another: add include:spf.mxproxy.dev to the existing one, before the ~all or -all. Two SPF records make both fail.
Delete the old MX records. Email goes to the answering MX with the lowest priority number: a leftover MX can receive part of the messages.
The whole DKIM. The value is long (it starts with v=DKIM1; k=rsa; p=). Copy it with the dashboard’s button and paste it without line breaks or extra spaces.
Domain in the name. If the panel adds the domain to the name by itself, type only _mxproxy; if you type _mxproxy.yourdomain.com, the record becomes _mxproxy.yourdomain.com.yourdomain.com.

Optional, but recommended

MTA-STS: CNAME mta-sts → mta-sts.mxproxy.dev and the two TXT records (_mta-sts and _smtp._tls) the dashboard shows. It makes the servers that send to you require TLS. We host the policy.
DMARC: TXT _dmarc with v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com to start by just watching. The reports arrive by email; the DMARC reader opens the files.

What is different at Squarespace Domains (formerly Google Domains)

Squarespace’s forwarding. Squarespace’s own email forwarding uses Mailgun MX and TXT records, which cannot be removed while a rule is active. Delete the forwarding rules first; Squarespace removes the records and then you create mxproxy’s.
Google Domains leftovers. Migrated domains may have old MX records from Google’s forwarding (names with google.com). Delete them.
One email service at a time. Squarespace does not take MX records of different services at once: if it reports a conflict, use Replace record.
Size and quotes. SPF and DKIM take keys up to 2048 bits without splitting; other TXT records go up to 255 characters (_mxproxy fits). Paste the values without quotes.
Where it applies. DNS is only edited there if the domain is registered at Squarespace or connected through its nameservers; otherwise, edit it at the nameservers’ provider.
Timing. A new record’s default TTL is 4 hours: a changed value may take that long to show.

Squarespace Domains’ official help

4. Check

Back in the mxproxy dashboard, click Verify now. Each record shows as ok or pending.

Want to check from the outside? Use the free checker, no sign-up:

Still pending? A DNS change usually takes minutes, but can take a few hours (until the old record’s TTL runs out). Wait and check again.

5. Choose where each address goes

Catch-all: all email to any address of the domain goes to the inbox you choose (your Gmail, for example). That is what the free plan offers: one domain, one destination, 10 messages a month.
Forwarders: one address per line (hello@ to you, billing@ to your accountant), with up to 10 destinations each, depending on the plan. From Personal up.

Send an email from another address to hello@yourdomain.com: it should arrive within seconds. The dashboard’s log shows each message.

6. Reply as the domain in Gmail

To reply as hello@yourdomain.com, and not as your personal address, Gmail needs an SMTP server: create a credential in the dashboard (paid plans, from Personal up) and add the address under Send mail as, with server smtp.mxproxy.dev, port 587. The step by step, for Gmail and Outlook, is in Reply from your domain.

If it does not work

MX pending: check that no old MX is left and that the name is the root (@ or blank, depending on the panel), not mx or www.
SPF pending: is there only one v=spf1 TXT, and does it contain include:spf.mxproxy.dev?
DKIM pending: the name is exactly the dashboard’s (with ._domainkey) and the value was pasted whole.
Nothing changes: where the domain is registered, look at its DNS servers (nameservers). If they are not Squarespace Domains’, the changes have to be made at the company of those servers.

Still stuck? Write to contato@mxproxy.dev.

Custom domain email in Gmail, with DNS at Squarespace Domains (formerly Google Domains)