How do I set up my custom sending domain?

A verified custom sending domain lets you send newsletters from your own email address and protects your deliverability. You can set one up at the channel level or on a company-level email connection.

Before you start

• Use a subdomain (for example, mail in mail.yourdomain.com). This keeps spam reports from affecting your root domain’s reputation.
• Your sender email and reply-to email should share the same root domain (for example, @mail.yourdomain.com and @reply.yourdomain.com).
• Manual replies (including a person’s out-of-office message) go to your reply-to address; some server-triggered automated replies go to the sender email.

Where to add your domain

• Channel level — open the channel’s Settings → Sending emails; the Sending Domain section is at the top.
• Company-level email connection — if your account sends through a company-level Letterhead connection, manage domains inside the connection setup instead. See Company-level email connection below.

Add and verify the domain

Letterhead sends via SparkPost. In the Sending Domain section:

1. Enter your sending subdomain (for example, mail.yourdomain.com).
2. Letterhead shows the DNS records to publish. Copy each Hostname and Value into your DNS provider (GoDaddy, Cloudflare, Namecheap, etc.):
   • CNAME record
   • DKIM record (a TXT record)
   • DMARC record (a TXT record)
3. Also confirm your SPF record includes SparkPost (see below). SPF isn’t shown as its own record card, but Letterhead still checks it as part of verification.
4. Back in Letterhead’s Sending Domain section, click Verify domain.
5. When the records are correct, each card shows a green Verified label instead of Verification needed.

Verification can take anywhere from a couple of minutes to a few hours. If your domain won’t verify, double-check the values; if problems persist, contact [email protected].

DNS provider quirks: some providers require a trailing dot on values (for example, sparkpostmail.com.) so your root domain isn’t appended, and some only want the subdomain portion as the hostname (for example, scph****._domainkey instead of the full hostname).

CNAME record

Create a new record with your DNS provider:

• Record Type: CNAME
• Hostname: the CNAME hostname copied from Letterhead (many providers only need the subdomain part, e.g. mail)
• Value: the CNAME value copied from Letterhead (e.g. sparkpostmail.com)

DKIM record

Create a new record:

• Record Type: TXT
• Hostname: the DKIM hostname from Letterhead — for a subdomain it looks like scph0####._domainkey.mail.yourdomain.com
• Value: the DKIM value from Letterhead (starts with v=DKIM1; k=rsa; h=sha256;...)

SPF record (required for deliverability)

SPF tells mailbox providers which servers may send email for your domain. Because Letterhead sends through SparkPost, your SPF record must include SparkPost — otherwise Gmail and other providers may reject or rate-limit your messages, and your newsletters may land in spam.

• You should only have one SPF record per domain. If one exists (it starts with v=spf1), merge SparkPost into it rather than creating a second record: add include:sparkpostmail.com to the existing value and save. Don’t replace your existing record unless your IT team says to.
• If none exists, create a TXT record on your root domain (hostname usually @ or blank) that includes include:sparkpostmail.com alongside any other services that legitimately send from your domain, for example:

v=spf1 include:_spf.google.com include:sparkpostmail.com ~all

DMARC record

DMARC tells receiving mail servers how to handle messages that claim to be from your domain but fail authentication, protecting you from spoofing.

• Record Type: TXT
• Hostname: _dmarc on your sending subdomain — for example, _dmarc.mail.yourdomain.com
• Value: must include v=DMARC1 and a policy tag (p=none, p=quarantine, or p=reject). Start new records with p=none so legitimate mail isn’t accidentally quarantined while you identify SPF/DKIM issues. We strongly recommend the rua tag so you receive aggregate reports:

v=DMARC1; p=none; rua=mailto:[email protected]

Separate tags with semicolons; rua and ruf accept multiple comma-separated addresses. You’ll begin receiving DMARC reports at that address, which help you spot authentication issues and malicious use of your domain. Advanced tags exist but aren’t recommended for initial setup.

Company-level email connection

If your account uses Letterhead’s email delivery as a company-level sending connection, you add and verify sending domains inside the connection setup rather than in a channel’s settings. Each connection has its own isolated sending identity, so its domains stay separate from other connections.

Availability

This is a newer capability that may need to be enabled for your account — contact [email protected] if you don’t see it.

1. Open your company settings and go to Settings → Sending.
2. Select (or create) your Letterhead email connection.
3. In the connection setup, add your sending subdomain — the same way as above.
4. Letterhead shows the CNAME, DKIM, and DMARC records to publish. Add them with your DNS provider, then click Verify domain.
5. You can re-verify a domain at any time, or remove domains you no longer need.

This is a company admin area. If you don’t see the email connection settings, ask your administrator.

Connecting an external ESP instead

If you sync audience data from another provider rather than (or alongside) sending through Letterhead:

• Mailchimp — enter your API Key (Mailchimp: Profile → Extras → API Keys), Audience (List) ID (Audience → Settings → Audience name and defaults), and Server Prefix (the us6 in https://us6.api.mailchimp.com/).
• Iterable — enter your Iterable API Key (Iterable: Integrations → API Keys).
• SendGrid and other providers may also be available as sending connections, depending on your account.

See Working in Integrations for more on connected services.

Related

• Working in Settings
• Manage sending domains for your company email connection
• What is BIMI and How to Set It Up