Deliverability

Deliverability is whether your mail lands in the inbox or the spam folder. Half of it is authentication — cryptographic proof that you are allowed to send as your domain — and MiniMailer sets that half up for you. The other half is behaviour: what you send, to whom, and how they react.

The three-letter acronyms, briefly

• SPF (Sender Policy Framework) — a DNS record listing which servers may send mail for a domain. Receivers check the connecting server against it.
• DKIM (DomainKeys Identified Mail) — a cryptographic signature on each message, verified against a public key in your DNS. Proves the message wasn't altered and really came from the domain.
• DMARC — the policy layer on top: tells receivers what to do when SPF/DKIM fail (nothing, quarantine, reject) and where to send aggregate reports.

Gmail, Microsoft, and Yahoo now effectively require all three for anyone sending at volume. Unauthenticated mail doesn't get a warning — it quietly underdelivers.

What MiniMailer configures for you

When you register a domain, the DNS records handed back are a complete authentication setup:

• DKIM with a dedicated 2048-bit key — each domain gets its own signing key pair; you publish the public half. 2048-bit is current best practice (1024-bit keys are considered weak). If a key is ever at risk, rotate it via the API (rotate_dkim_key) without re-verifying the domain.
• A custom MAIL FROM subdomain (default send.yourdomain) with its MX and SPF records — this aligns the bounce-handling domain with your domain rather than the infrastructure's, which is what DMARC alignment requires.
• A DMARC record to publish — starting at p=quarantine so receivers act on failures.
• TLS required by default — messages are delivered over encrypted connections; you can relax the policy per domain to optional only if a recipient's legacy server forces it.

Verification then runs automatically every 15 minutes, per record — the API's records endpoint shows exactly which records are still pending.

What stays your job

Authentication earns you the right to a reputation; behaviour decides what it is.

• Send to people who asked. Purchased lists and stale addresses drive the bounce and complaint rates that kill deliverability — see bounces and complaints.
• Warm up new domains. A fresh domain has no history; ramp volume gradually rather than sending 50,000 emails on day one.
• Split transactional and marketing traffic onto separate domains (the purpose field at registration). Receipts and password resets shouldn't inherit a newsletter's reputation.
• Keep engagement up. Receivers score senders on opens, replies, and deletions-without-reading. Cut recipients who never engage before they cut you.
• Make unsubscribing trivial. MiniMailer handles the one-click unsubscribe plumbing; a clean opt-out is always better for your reputation than a spam complaint.

When something's off

The dashboard's deliverability view tracks delivery, bounce, and complaint rates per domain; the domain.reputation_warning webhook tells your systems the moment monitored metrics degrade, and domain.reputation_recovered when they normalise. How reputation is monitored →