Blackmail is a Go package to send emails.

Import the library as zgo.at/blackmail; API docs: https://godocs.io/zgo.at/blackmail

There is also a smtp client library at zgo.at/blackmail/smtp which can be used without the main blackmail client if you want. It's a modified version of net/smtp (via go-smtp, with some changes).

There is a small commandline utility at cmd/blackmail.

Example

// Send a new message using blackmail.DefaultMailer
err := blackmail.Send("Send me bitcoins or I will leak your browsing history!",
    blackmail.From("", "blackmail@example.com"),
    blackmail.To("Name", "victim@example.com"),
    blackmail.Bodyf("I can haz ur bitcoinz?"))
// A more complex message with a text and HTML part and inline image.
err = blackmail.Send("I saw what you did last night 😏",
    blackmail.From("😏", "blackmail@example.com"),
    append(blackmail.To("Name", "victim@example.com"), blackmail.Cc("Other", "other@example.com")...),
    blackmail.Text("Text part")
    blackmail.HTML("HTML part: <img src="cid:blackmail:1">",
        blackmail.InlineImage("image/png", "logo.png", imgbytes)))
// You can create your own (re-usable) mailer.
mailer := blackmail.NewMailer("smtp://user:pass@localhost:25")
err = mailer.Send([..])
// Add some options to your mailer.
mailer = blackmail.NewMailer("smtp://user:pass@localhost:25
    blackmail.MailerAuth(..),
    blackmail.MailerTLS(&tls.Config{}),
    blackmail.RequireSTARTLS(true))
// Get RF5322 message with a list of recipients to send it to (To + Cc + Bcc).
msg, to := blackmail.Message([.. same arguments as Send() ..])

See the test cases in blackmail_test.go for various other examples.

Questions you may have

I get the error "tls: first record does not look like a TLS handshake"

You are attempting to establish a TLS connection to a server which doesn't support TLS or only supports it via the STARTTLS command.

I get the error "x509: certificate signed by unknown authority"

The certificate chain used for the TLS connection is not signed by a known authority. It's a self-signed certificate or you don't have the root certificates installed.

How can I use a @ in my username?

Encode as %40:

smtp://martin%40arp242.net:PASS@smtp.example.com:587'