github.com/cesbit/mailyak/v3

An elegant MIME mail library with support for attachments

A simple, easy to use email library for Go (golang).

• Full attachment support (attach anything that implements io.Reader)
• Send to multiple addresses at the same time, including BCC addresses.
• Supports composing multi-part messages (HTML and plain text emails for older clients)
• Write templates directly to the email body (implements io.Writer for convenience)
• Production ready - several million emails sent in a production environment
• SMTP over TLS support, with automatic STARTTLS upgrades for plaintext connections

Installation

If you're using go mod:

go get -v github.com/cesbit/mailyak/v3

Or with GOPATH:

go get -v github.com/cesbit/mailyak

Usage

// Create a new email - specify the SMTP host:port and auth (if needed)
mail := mailyak.New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

mail.To("[e-mail]")
mail.From("[e-mail]")
mail.FromName("Bananas for Friends")

mail.Subject("Business proposition")

// mail.HTML() and mail.Plain() implement io.Writer, so you can do handy things like
// parse a template directly into the email body
if err := t.ExecuteTemplate(mail.HTML(), "htmlEmail", data); err != nil {
    panic(" 💣 ")
}

// Or set the body using a string setter
mail.Plain().Set("Get a real email client")

// And you're done!
if err := mail.Send(); err != nil {
    panic(" 💣 ")
}

To send an attachment:

mail := mailyak.New("mail.host.com:25", smtp.PlainAuth("", "user", "pass", "mail.host.com"))

mail.To("[e-mail]")
mail.From("[e-mail]")
mail.Subject("I am a teapot")
mail.HTML().Set("Don't panic")

// input can be a bytes.Buffer, os.File, os.Stdin, etc.
// call multiple times to attach multiple files
mail.Attach("filename.txt", &input)

if err := mail.Send(); err != nil {
    panic(" 💣 ")
}

Notes

• Why "MailYak"? Because "MailyMcMailFace" is annoyingly long to type.
• You can use a single instance of mailyak to send multiple emails after changing the to/body/whatever fields, avoiding unnecessary allocation/GC pressure.
• Attachments are read when you call Send() to prevent holding onto multiple copies of the attachment in memory (source and email) - this means changing the attachment data between calling Attach() and Send() will change what's emailed out!
• For your own sanity you should vendor this, and any other libraries when going into production.