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Which SMTP service should I use to send email from my app or website?

Refresh runs an SMTP relay at smtp.f5send.com on port 465 with implicit TLS, and it accepts mail from any app, website or mail server. The API key id is the username and the key is the password; each message gets the API limits, suppression and logs.

What you get

  • Each accepted message becomes one API send. The API key, rate limit, domain check, suppression and request log all apply.
  • Port 465 uses implicit TLS 1.2 or 1.3 with a public certificate. The relay offers no STARTTLS and no port 587 or 25.
  • There is no separate SMTP password. The username is the API key id and the password is the key.
  • Settings → SMTP in the console gives ready configuration for Postfix, WP Mail SMTP, Python, Node.js and .NET.
  • A Test key simulates delivery over SMTP, the same as over HTTP. Test your app before it sends real mail.
  • Five failed logins in 10 minutes block that IP or key id for 10 minutes.
  • If the relay is down, your mail server keeps each message in its own queue and tries again.

How it works

  1. Verify your sending domain in Refresh. The relay sends only from a domain with status Verified.
  2. Mint an API key. Open Settings → SMTP to copy the key id and a ready configuration.
  3. Set host smtp.f5send.com, port 465, the key id as username and the key as password.
  4. Send a message with a Test key first. Then change to a Live key.

Documentation

Create a free account: 3,000 emails a month, unlimited domains, no card.

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