Glossary
Mail Server — SMTP, MTA, and MX
A mail server is a computer system that sends, receives, and stores email. Mail servers use SMTP (Simple Mail Transfer Protocol) for sending and relaying email, and IMAP or POP3 for client access. Every domain that receives email needs at least one mail server identified by an MX (Mail Exchanger) DNS record. Properly configured mail servers require SPF, DKIM, DMARC, and PTR records for reliable email delivery.
Types of Mail Servers
MTA (Mail Transfer Agent): sends and receives email between servers. Examples: Postfix, Exim, Sendmail.
MDA (Mail Delivery Agent): delivers email to local mailboxes. Examples: Dovecot, Procmail.
MUA (Mail User Agent): the client users read email in. Examples: Gmail, Outlook, Thunderbird.
Self-Hosted vs Cloud
Cloud providers (Google Workspace, Microsoft 365) handle server management. Self-hosted servers require manual configuration of all DNS records and ongoing maintenance.
Verify DNS for mail
Open DNS Preflight →FAQ
What is a mail server?
A system that sends, receives, and stores email using SMTP. Identified in DNS by MX records.
What DNS records does a mail server need?
MX (to receive), SPF (authorise senders), DKIM (sign email), DMARC (enforce policy), and PTR (reverse DNS for the sending IP).
Do I need a mail server to send email?
No — you can use a cloud email provider like Google Workspace or a sending service like SendGrid without running your own mail server.