hub · deliverability

Deliverability and authentication

Picking a great provider is necessary but not sufficient. Inbox placement depends on authentication (SPF, DKIM, DMARC), warming, suppressions, and engagement. Google and Yahoo's February 2024 bulk-sender requirements made authentication mandatory for any sender pushing more than 5,000 messages a day to either provider.

authentication

SPF · DKIM · DMARC · BIMI

SPF

A DNS record listing which servers may send for your domain.

DKIM

A cryptographic signature attached to outbound mail.

DMARC

A policy that tells mailbox providers what to do when SPF or DKIM fail.

BIMI

A standard for showing your logo next to authenticated mail.

operations

Reputation and IP management

IP warming

Gradually ramping volume on a new IP to build reputation.

Dedicated IP

A sending IP reserved for one customer.

Shared IP

A sending IP used by many customers of a provider.

Suppressions

A list of recipients the provider refuses to send to.

Sandbox mode

A starter mode that limits sending to verified addresses.

checklist

Pre-launch deliverability checklist

01 Publish SPF for the sending domain. Validate with mxtoolbox or a provider tool.
02 Enable DKIM signing on the provider and add the public key to DNS.
03 Publish DMARC at p=none with an rua report address you control.
04 Verify the record in production by sending to a Gmail and Outlook address you can inspect headers on.
05 After two to four weeks of clean DMARC reports, tighten the policy to p=quarantine, then p=reject.
06 Send only to recipients who consented. Honor unsubscribe requests within 24 hours per CAN-SPAM.
07 Suppress hard bounces immediately. Most providers do this for you; verify it is on.
08 For volumes above 5,000/day to Gmail or Yahoo, confirm one-click List-Unsubscribe is configured.