Send e-mail over smtp and change the sender's name

I am sending e-mails over smtp in golang, which works perfectly fine. To set the sender of an e-mail I use the Client.Mail funtion:

func (c *Client) Mail(from string) error

When the recipient gets the e-mail he sees the sender as plaintext e-mail address: sender@example.com

I want the sender to be displayed like: Sandy Sender <sender@example.com>.

Is this possible? I tried setting the sender to Sandy Sender <sender@example.com> or only Sandy Sender but none of them work. I get the error 501 5.1.7 Invalid address

You need to set the From field of your mail to Sandy Sender <sender@example.com>:

...
From: Sandy Sender <sender@example.com>
To: recipient@example.com
Subject: Hello!

This is the body of the message.

And use the address only (sender@example.com) in Client.Mail.

Alternatively, you can use my package Gomail:

package main

import (
    "gopkg.in/gomail.v2"
)

func main() {
    m := gomail.NewMessage()
    m.SetAddressHeader("From", "sender@example.com", "Sandy Sender")
    m.SetAddressHeader("To", "recipient@example.com")
    m.SetHeader("Subject", "Hello!")
    m.SetBody("text/plain", "This is the body of the message.")

    d := gomail.NewPlainDialer("smtp.example.com", 587, "user", "123456")

    if err := d.DialAndSend(m); err != nil {
        panic(err)
    }
}