Email deliverability
Whether the email your product sends lands in inboxes rather than spam, which depends on signed mail, sending reputation and how fast volume grows.
Updated October 2026 · with examples from our own builds
What does email deliverability mean in practice?
Mail providers judge every message by who sent it and how that sender has behaved. Domains need SPF, DKIM and DMARC records so receivers can verify mail is genuine; new mailboxes need to warm up slowly; and high bounce or complaint rates push future mail into spam.
Receipts and password resets depend on it, and any product that sends outreach depends on it heavily. The failures are quiet: nothing errors, open rates fall, and a blocklisted domain can take weeks to recover.
Compliance sits alongside it. Marketing mail needs a working unsubscribe and a postal address, and an address that opted out must never be written to again.
Email deliverability at a glance
- DNS records
- SPF, DKIM and DMARC on every sending domain
- New mailbox rule
- Start low and ramp up gradually
- Legal basics
- One-click unsubscribe and a suppression list
Where has email deliverability come up in our builds?
A June 2026 review found the first send path told users to publish a DKIM record holding a placeholder key, sent mail unsigned and never called its warmup logic. Each sending domain now gets its own RSA-2048 key, verification checks that the published key matches, new mailboxes ramp from 10 to 35 sends a day under a hard ceiling of 50, and a seven-day bounce rate of 2% or more halves a mailbox's cap.
Common questions about email deliverability
Why are my app's emails going to spam?
Check that the sending domain publishes SPF, DKIM and DMARC records and that mail is actually signed with the key the DKIM record holds. Then look at volume: a new domain or mailbox that sends a lot on day one looks suspicious.
Should cold outreach go out from my product's main domain?
It puts transactional mail such as receipts and password resets at risk if outreach harms the domain's reputation. Many teams send outreach from separate domains and mailboxes, warmed up gradually.
Related terms
Sources
Planning a product and not sure where email deliverability fits? Ask us, or browse all 116 terms in the glossary.