Email deliverability

Email deliverability is the rate at which sent messages reach the recipient's primary inbox — distinct from delivery (the recipient mail server accepted the message, regardless of whether it landed in inbox or spam folder) and from send (your platform handed the message to the sending pipeline). A message can be sent successfully, delivered to the recipient mail server, and end up in the spam folder — that is a delivery success and a deliverability failure. Open rate, click rate, and conversion all depend on deliverability, not delivery.

Mailbox providers run a multi-stage scoring pipeline against every incoming message. Six factors dominate the output:

1. Authentication — SPF, DKIM, DMARC alignment.
2. IP reputation — historical bounce / complaint / engagement record on the sending IP.
3. Domain reputation — same, on the From-domain (separate signal from IP).
4. Engagement — recipient open / click / reply behaviour on prior sends.
5. List hygiene — bounce rate, complaint rate, suppression-list discipline. Double opt-in is the largest lever here.
6. Content — spam-keyword density, link reputation, image-to-text ratio.

Stages 1, 2, and 5 are operator responsibilities you can directly tune; 3 and 4 are emergent properties of doing 1, 2, and 5 well; 6 is editorial. Getting 1, 2, and 5 right takes a typical commercial sender from 60-80% inboxing to 95%+.

• Authentication: AcelleMail does not sign SPF/DKIM itself — those are DNS / vendor responsibilities. Sending drivers (SES, Mailgun, SparkPost, etc.) handle DKIM signing on the vendor side; the operator publishes SPF + DMARC TXT records in DNS.
• Reputation: built-in IP warmup engine (WarmupStrategy model) ramps volume on new IPs. Per-server delivery / bounce / complaint analytics are visible in the admin dashboard.
• Bounce + complaint handling: webhook receivers for SES, Mailgun, SparkPost convert vendor events into BounceLog rows; the hard-bounce path auto-blacklists, the soft-bounce path accumulates.
• List hygiene: per-list subscribe_confirmation flag (double opt-in), suppression list, NeverBounce / ZeroBounce verification adapters under app/Library/Everification/.

This entry is the index card. The full 24-minute pillar guide — RFC syntax, IP warmup schedules, BIMI, bounce-handler tuning, troubleshooting playbook — is at /guide/email-deliverability. Read that guide if you are responsible for the deliverability of a real production list.