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Squarespace + MailKite

Squarespace sites can send email through external SMTP for transactional notifications. Point it at MailKite for DKIM-signed delivery on your own domain.

What you need

A verified domain with SPF + DKIM published
Your API key (mk_live_…)
Squarespace site with Commerce or a plan that supports external SMTP

Configure SMTP

Open your Squarespace dashboard and navigate to Settings → Advanced → External SMTP. Enter the MailKite connection details.

SMTP Host	`smtp.mailkite.dev`
SMTP Port	`587`
Encryption	TLS (STARTTLS)
Username	`mailkite`
Password	Your API key (`mk_live_…`)
From Address	`hello@yourdomain.com` (on a verified domain)

External SMTP Settings

# Settings → Advanced → External SMTP

SMTP Server:    smtp.mailkite.dev
Port:           587
Username:       mailkite
Password:       mk_live_...
From Address:   hello@yourdomain.com

Test it

Submit a form on your Squarespace site or use Squarespace's built-in email test to verify the connection. Check your MailKite dashboard to confirm the message was relayed.

Troubleshooting

Emails not sending — confirm the From address is on a verified domain.
535 Authentication failed — your password must be your mk_live_… API key, not a separate SMTP password.
External SMTP not available — this is a premium feature; verify your Squarespace plan supports it. Commerce plans include it by default.

See the SMTP relay docs for the full connection reference, or all integrations for other platforms.