email sending library

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The library is a wrapper around the stdlib net/smtp simplifying email sending. It supports authentication, SSL/TLS,
user-specified SMTP servers, content-type, charset, multiple recipients and more.

Usage example:

client := email.NewSender("localhost", email.ContentType("text/html"), email.Auth("user", "pass"))
err := client.Send("<html>some content, foo bar</html>", 
	email.Params{From: "[email protected]", To: []string{"[email protected]"}, Subject: "Hello world!"})


NewSender accepts a number of options to configure the client:

  • Port: SMTP port (default: 25)
  • TLS: Use TLS SMTP (default: false)
  • Auth(user, password): Username and password for SMTP authentication (default: empty, no authentication)
  • ContentType: Content type for the email (default: “text/plain”)
  • Charset: Charset for the email (default: “utf-8”)
  • TimeOut: Timeout for the SMTP connection (default: 30 seconds)
  • Log: Logger to use (default: no logging)
  • SMTP: Set custom smtp client (default: none)

See go docs for Option functions.

Options should be passed to NewSender after the mandatory first (host) parameter.

sending email

To send email user need to create a sender first and then use Send method. The method accepts two parameters:

  • email content (string)
  • parameters (email.Params)

    type Params struct {
        From    string   // From email field
        To      []string // From email field
        Subject string   // Email subject

See go docs for Send function.

technical details

  • Content-Transfer-Encoding set to quoted-printable
  • Custom SMTP client (smtp.Client from stdlib) can be set by user with SMTP option. In this case it will be used instead of making a new smtp client internally.
  • Logger can be set with Log option. It should implement email.Logger interface with a single Logf(format string, args ...interface{}) method. By default, “no logging” internal logger is used. This interface is compatible with the go-pkgz/lgr logger.
  • The library has no external dependencies, except for testing. It uses the stdlib net/smtp package.
  • SSL/TLS supported with TLS option. Pls note: this is not the same as STARTTLS (not supported) which is usually on port 587 vs SSL/TLS on port 465.


This library is not intended to be used for sending emails with attachments or sending a lot of massive emails with
low latency requirements. The intended use case is sending simple messages, like alerts, notification and so on.
For example, sending alerts from a monitoring system, or for authentication-related emails, i.e. “password reset email”,
“verification email”, etc.


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