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sender.go
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sender.go
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package mailsender
import (
"encoding/base64"
"fmt"
"net/mail"
"net/smtp"
"strings"
"time"
)
// Smp represent SMTP server mail sender
type Smtp struct {
Addr string
}
// NewSmtp create new SMTP mail sender
func NewSmtp(addr string) *Smtp {
return &Smtp{Addr: addr}
}
// Send send mail with SMTP server
func (s *Smtp) Send(from, to, subject, body string) error {
// Connect to the remote SMTP server.
c, err := smtp.Dial(s.Addr)
if err != nil {
return err
}
// Set the sender and recipient first
if err := c.Mail(from); err != nil {
return err
}
if err := c.Rcpt(to); err != nil {
return err
}
// Send the email body.
wc, err := c.Data()
if err != nil {
return err
}
msg := composeMimeMail(to, from, subject, body)
if _, err := wc.Write(msg); err != nil {
return err
}
if err = wc.Close(); err != nil {
return err
}
if err = c.Quit(); err != nil {
return err
}
return nil
}
// compose mail body
func composeMimeMail(to string, from string, subject string, body string) []byte {
header := make(map[string]string)
header["From"] = formatEmailAddress(from)
header["To"] = formatEmailAddress(to)
header["Subject"] = encodeRFC2047(subject)
header["MIME-Version"] = "1.0"
header["Content-Type"] = "text/plain; charset=\"utf-8\""
header["Content-Transfer-Encoding"] = "base64"
header["Date"] = time.Now().String()
message := ""
for k, v := range header {
message += fmt.Sprintf("%s: %s\r\n", k, v)
}
base64Text := make([]byte, base64.StdEncoding.EncodedLen(len(body)))
base64.StdEncoding.Encode(base64Text, []byte(body))
message += "\r\n" + string(base64Text)
return []byte(message)
}
// Never fails, tries to format the address if possible
func formatEmailAddress(addr string) string {
e, err := mail.ParseAddress(addr)
if err != nil {
return addr
}
return e.String()
}
// encode string to rfc2047
func encodeRFC2047(str string) string {
// use mail's rfc2047 to encode any string
addr := mail.Address{Address: str}
return strings.TrimSuffix(strings.Trim(addr.String(), " <>"), "@")
}