Email delivery guide
What is SMTP relay?
SMTP relay is a service that sends outbound email for another server, application, website, printer, or device. It is useful when you need reliable sending, authentication, or a workaround for blocked SMTP ports.
Outbound
SMTP relay handles mail leaving your system, not mail arriving in your inbox.
Authenticated
Your app or server logs in before it is allowed to send through the relay.
Useful
Common for port 25 blocks, apps, scanners, websites, and self-hosted mail servers.
How SMTP relay works
- 1. Your system connectsYour app, device, or server connects to the relay with SMTP credentials.
- 2. The relay accepts mailThe relay checks authentication and the sending domain before accepting the message.
- 3. The relay delivers itThe relay sends the message onward to the recipient's mail server.
When you need SMTP relay
- Your ISP or hosting provider blocks outbound port 25.
- A website or application needs to send transactional email.
- A printer, camera, NAS, or alerting system needs SMTP sending.
- You run your own mail server but want another service to handle outbound delivery.
SMTP relay vs email hosting
SMTP relay sends mail. Email hosting stores mailboxes and gives users ways to read messages through Webmail, IMAP, or POP3. Some businesses need both, but they solve different parts of the email puzzle.
Need help sending email reliably?
DNSExit SMTP Relay supports authenticated sending for business email, applications, devices, and port-blocked networks.