Authentication and Deliverability

Your sender domain is what inbox providers learn to trust. Authentication proves that your email delivery service is allowed to send email for your domain.

An email can include several sender-related addresses. Each address has a separate role for delivery, authentication, or replies.

DNS records identify your domain. Reverse DNS helps inbox providers check that a sending IP address has a valid hostname.

Message headers, MIME structure, and basic formatting rules help inboxes read, display, and trust an email.

SPF is a DNS record that lists the servers and services that may send email for your domain.

DKIM adds a signature to each email so inboxes can confirm that an approved domain accepted responsibility for the message.

DMARC tells inboxes how to handle a message that uses your domain but does not pass aligned SPF or DKIM checks.

DMARC alignment checks whether SPF or DKIM authentication uses the same domain family as the domain subscribers see in the From address.

TLS encrypts email while it moves between mail systems. Bulk senders are now expected to use TLS.

MTA-STS and TLS reporting are advanced controls for domains that need stronger protection for inbound email transport.

ARC helps forwarding services preserve email authentication results when forwarding breaks SPF or changes a message.

Sender reputation is the trust inbox providers build from your authentication, sending history, volume, complaints, and subscriber behavior.

Shared IPs let many senders use the same sending infrastructure. Dedicated IPs place more reputation responsibility on one sender.

New senders should build trust gradually instead of sending a large campaign right away.

Inbox providers may distrust a sender because of the sending IP, domain, email delivery service account, or links in the email.

Open tracking, click tracking, tracking domains, and UTM fields affect reporting. They can also affect whether subscribers trust your email.

Delivery means the receiving system accepted the message. Placement means where the inbox shows the message.

Marketing emails should make unsubscribing easy. Bulk sender rules also expect fast, simple unsubscribe handling.

A bounce means an email could not be delivered. Repeatedly sending to bad addresses can hurt future delivery.

A complaint means a subscriber marked your email as spam. Inbox providers treat complaints as one of the strongest negative signals.

Feedback loops tell senders when subscribers mark email as spam. These reports usually come from an email delivery service or mailbox provider.

Suppression protects people who should not receive normal marketing email, including unsubscribed, bounced, or complained subscribers.

BIMI can show a brand logo in some inboxes, but logo display depends on strong authentication and inbox support.