Deliverability checklist

Practical steps that keep transactional mail out of spam folders: authenticate your domain, format messages well, and warm up new senders.

Prerequisite: Domain & authorized senders and Setting up your email account.

1. Authenticate your domain (SPF + DKIM)

Verify your domain and authorize senders in the go.routee.net portal. Verification publishes the SPF and DKIM DNS records that let receivers trust your mail.

• The From address must be a verified authorized sender on a verified domain.
• An unverified sender is rejected with 000002 (see Email error codes).

📘

SPF and DKIM are the supported domain-authentication methods. Details: Domain & authorized senders.

👍

DMARC is a DNS policy you publish yourself (a _dmarc TXT record). It isn't a Routee API feature, but adding it once SPF and DKIM pass improves inbox placement.

2. Send multipart (text + HTML)

Always include a plain-text alternative alongside HTML. HTML-only messages look like spam to many filters.

{
  "content": {
    "html": "<p>Your order <strong>#1234</strong> has shipped.</p>",
    "text": "Your order #1234 has shipped."
  }
}

Keep the two versions equivalent — mismatched text and HTML is a spam signal.

3. Subject and body hygiene

4. Add a List-Unsubscribe header

Even for transactional mail, a working unsubscribe path reduces spam complaints and is expected by major mailbox providers. Provide both header forms:

List-Unsubscribe: <mailto:[email protected]>, <https://yourdomain.com/unsubscribe?u=123>
List-Unsubscribe-Post: List-Unsubscribe=One-Click

5. Warm up new domains and senders

New sending domains have no reputation. Ramp volume gradually over days to weeks:

• Start with your most engaged, most reliable recipients.
• Increase daily volume steadily rather than spiking.
• Watch bounce and complaint rates as you scale (see Handle bounces & interpret statuses).

Pre-send checklist

• Domain verified; SPF + DKIM passing
• From is a verified authorized sender
• DMARC policy published in DNS
• Both html and text content set
• Clear subject; footer identifies the sender
• List-Unsubscribe header present
• New domain? Warmup plan in place

Next steps

• Handle bounces & interpret statuses — monitor reputation after you send
• Domain & authorized senders — SPF/DKIM setup detail
• Send your first transactional email — put it into practice

Related

• Setting up your email account
• Transactional Email — overview