Email

Every email your company sends or receives goes through SMTP. You need this to configure mail servers, debug delivery failures, and understand SPF/DKIM/DMARC.

The structure of every email header you've ever seen is defined here. Essential for email deliverability debugging and understanding DKIM header signing.

Your email client (Outlook, Gmail app, Thunderbird, Apple Mail) uses IMAP or JMAP to read mail. Essential for mail server configuration and client integration.

Without a correct SPF record, your domain's email will fail or be deferred by major receivers (Gmail, Outlook). Set correctly as part of basic email deliverability.

DKIM is required to pass DMARC. Without it, your email won't be trusted by major providers. Set up alongside SPF as part of any serious email configuration.

DMARC is the final layer of email authentication. Without it, your domain can be spoofed in phishing. Google and Yahoo require DMARC for bulk senders.