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Go Simple Mail
The best way to send emails in Go with SMTP Keep Alive and Timeout for Connect and Send.
IMPORTANT
Examples in this README are for v2.2.0 and above. Examples for older versions can be found here.
Go 1.13+ is required.
Breaking change in 2.2.0: The signature of SetBody and AddAlternative used
to accept strings ("text/html" and "text/plain") and not require on of the
contentType constants (TextHTML or TextPlain). Upgrading, while not
quite following semantic versioning, is quite simple:
email := mail.NewMSG()
- email.SetBody("text/html", htmlBody)
- email.AddAlternative("text/plain", plainBody)
+ email.SetBody(mail.TextHTML, htmlBody)
+ email.AddAlternative(mail.TextPlain, plainBody)
Introduction
Go Simple Mail is a simple and efficient package to send emails. It is well tested and documented.
Go Simple Mail can only send emails using an SMTP server. But the API is flexible and it is easy to implement other methods for sending emails using a local Postfix, an API, etc.
This package contains (and is based on) two packages by Joe Grasse:
- https://github.com/joegrasse/mail (unmaintained since Jun 29, 2018), and
- https://github.com/joegrasse/mime (unmaintained since Oct 1, 2015).
A lot of changes in Go Simple Mail were sent with not response.
Features
Go Simple Mail supports:
- Multiple Attachments with path
- Multiple Attachments in base64
- Multiple Attachments from bytes (since v2.6.0)
- Inline attachments from file, base64 and bytes (bytes since v2.6.0)
- Multiple Recipients
- Priority
- Reply to
- Set sender
- Set from
- Allow sending mail with different envelope from (since v2.7.0)
- Embedded images
- HTML and text templates
- Automatic encoding of special characters
- SSL/TLS and STARTTLS
- Unencrypted connection (not recommended)
- Sending multiple emails with the same SMTP connection (Keep Alive or Persistent Connection)
- Timeout for connect to a SMTP Server
- Timeout for send an email
- Return Path
- Alternative Email Body
- CC and BCC
- Add Custom Headers in Message
- Send NOOP, RESET, QUIT and CLOSE to SMTP client
- PLAIN, LOGIN and CRAM-MD5 Authentication (since v2.3.0)
- AUTO Authentication (since v2.14.0)
- Allow connect to SMTP without authentication (since v2.10.0)
- Custom TLS Configuration (since v2.5.0)
- Send a RFC822 formatted message (since v2.8.0)
- Send from localhost (yes, Go standard SMTP package cannot do that because... WTF Google!)
- Support text/calendar content type body (since v2.11.0)
- Support add a List-Unsubscribe header (since v2.11.0)
- Support to add a DKIM signarure (since v2.11.0)
- Support to send using custom connection, ideal for proxy (since v2.15.0)
- Support Delivery Status Notification (DSN) (since v2.16.0)
- Support text/x-amp-html content type body (since v2.16.0)
Documentation
https://pkg.go.dev/github.com/xhit/go-simple-mail/v2?tab=doc
Note 1: by default duplicated recipients throws an error, from v2.13.0 you can use email.AllowDuplicateAddress = true to avoid the check.
Note 2: by default Bcc header is not set in email. From v2.14.0 you can use email.AddBccToHeader = true to add this.
Note 3: by default all addresses are validated against RFC5322. Setting email.UseProvidedAddress = true skips this validation, but requires you to ensure a valid address is sent.
Download
This package uses go modules.
$ go get github.com/xhit/go-simple-mail/v2
Usage
package main
import (
"log"
mail "github.com/xhit/go-simple-mail/v2"
"github.com/toorop/go-dkim"
)
const htmlBody = `<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Hello Gophers!</title>
</head>
<body>
<p>This is the <b>Go gopher</b>.</p>
<p><img src="https://raw.githubusercontent.com/xhit/go-simple-mail/master/cid:Gopher.png" alt="Go gopher" /></p>
<p>Image created by Renee French</p>
</body>
</html>`
const privateKey = `-----BEGIN RSA PRIVATE KEY-----
MIIEpAIBAAKCAQEAwGrscUxi9zEa9oMOJbS0kLVHZXNIW+EBjY7KFWIZSxuGAils
wBVl+s5mMRrR5VlkyLQNulAdNemg6OSeB0R+2+8/lkHiMrimqQckZ5ig8slBoZhZ
wUoL/ZkeQa1bacbdww5TuWkiVPD9kooT/+TZW1P/ugd6oYjpOI56ZjsXzJw5pz7r
DiwcIJJaaDIqvvc5C4iW94GZjwtmP5pxhvBZ5D6Uzmh7Okvi6z4QCKzdJQLdVmC0
CMiFeh2FwqMkVpjZhNt3vtCo7Z51kwHVscel6vl51iQFq/laEzgzAWOUQ+ZEoQpL
uTaUiYzzNyEdGEzZ2CjMMoO8RgtXnUo2qX2FDQIDAQABAoIBAHWKW3kycloSMyhX
EnNSGeMz+bMtYwxNPMeebC/3xv+shoYXjAkiiTNWlfJ1MbbqjrhT1Pb1LYLbfqIF
1csWum/bjHpbMLRPO++RH1nxUJA/BMqT6HA8rWpy+JqiLW9GPf2DaP2gDYrZ0+yK
UIFG6MfzXgnju7OlkOItlvOQMY+Y501u/h6xnN2yTeRqXXJ1YlWFPRIeFdS6UOtL
J2wSxRVdymHbGwf+D7zet7ngMPwFBsbEN/83KGLRjkt8+dMQeUeob+nslsQofCZx
iokIAvByTugmqrB4JqhNkAlZhC0mqkRQh7zUFrxSj5UppMWlxLH+gPFZHKAsUJE5
mqmylcECgYEA8I/f90cpF10uH4NPBCR4+eXq1PzYoD+NdXykN65bJTEDZVEy8rBO
phXRNfw030sc3R0waQaZVhFuSgshhRuryfG9c1FP6tQhqi/jiEj9IfCW7zN9V/P2
r16pGjLuCK4SyxUC8H58Q9I0X2CQqFamtkLXC6Ogy86rZfIc8GcvZ9UCgYEAzMQZ
WAiLhRF2MEmMhKL+G3jm20r+dOzPYkfGxhIryluOXhuUhnxZWL8UZfiEqP5zH7Li
NeJvLz4pOL45rLw44qiNu6sHN0JNaKYvwNch1wPT/3/eDNZKKePqbAG4iamhjLy5
gjO1KgA5FBbcNN3R6fuJAg1e4QJCOuo55eW6vFkCgYEA7UBIV72D5joM8iFzvZcn
BPdfqh2QnELxhaye3ReFZuG3AqaZg8akWqLryb1qe8q9tclC5GIQulTInBfsQDXx
MGLNQL0x/1ylsw417kRl+qIoidMTTLocUgse5erS3haoDEg1tPBaKB1Zb7NyF8QV
+W1kX2NKg5bZbdrh9asekt0CgYA6tUam7NxDrLv8IDo/lRPSAJn/6cKG95aGERo2
k+MmQ5XP+Yxd+q0LOs24ZsZyRXHwdrNQy7khDGt5L2EN23Fb2wO3+NM6zrGu/WbX
nVbAdQKFUL3zZEUjOYtuqBemsJH27e0qHXUls6ap0dwU9DxJH6sqgXbggGtIxPsQ
pQsjEQKBgQC9gAqAj+ZtMXNG9exVPT8I15reox9kwxGuvJrRu/5eSi6jLR9z3x9P
2FrgxQ+GCB2ypoOUcliXrKesdSbolUilA8XQn/M113Lg8oA3gJXbAKqbTR/EgfUU
kvYaR/rTFnivF4SL/P4k/gABQoJuFUtSKdouELqefXB+e94g/G++Bg==
-----END RSA PRIVATE KEY-----`
func main() {
server := mail.NewSMTPClient()
// SMTP Server
server.Host = "smtp.example.com"
server.Port = 587
server.Username = "[email protected]"
server.Password = "examplepass"
server.Encryption = mail.EncryptionSTARTTLS
// You can specified authentication type:
// - AUTO (default)
// - PLAIN
// - LOGIN
// - CRAM-MD5
// - None
// server.Authentication = mail.AuthAuto
// Variable to keep alive connection
server.KeepAlive = false
// Timeout for connect to SMTP Server
server.ConnectTimeout = 10 * time.Second
// Timeout for send the data and wait respond
server.SendTimeout = 10 * time.Second
// Set TLSConfig to provide custom TLS configuration. For example,
// to skip TLS verification (useful for testing):
server.TLSConfig = &tls.Config{InsecureSkipVerify: true}
// SMTP client
smtpClient,err := server.Connect()
if err != nil{
log.Fatal(err)
}
// New email simple html with inline and CC
email := mail.NewMSG()
email.SetFrom("From Example <[email protected]>").
AddTo("[email protected]").
AddCc("[email protected]").
SetSubject("New Go Email").
SetListUnsubscribe("<mailto:[email protected]?subject=https://example.com/unsubscribe>")
email.SetBody(mail.TextHTML, htmlBody)
// also you can add body from []byte with SetBodyData, example:
// email.SetBodyData(mail.TextHTML, []byte(htmlBody))
// or alternative part
// email.AddAlternativeData(mail.TextHTML, []byte(htmlBody))
// add inline
email.Attach(&mail.File{FilePath: "/path/to/image.png", Name:"Gopher.png", Inline: true})
// also you can set Delivery Status Notification (DSN) (only is set when server supports DSN)
email.SetDSN([]mail.DSN{mail.SUCCESS, mail.FAILURE}, false)
// you can add dkim signature to the email.
// to add dkim, you need a private key already created one.
if privateKey != "" {
options := dkim.NewSigOptions()
options.PrivateKey = []byte(privateKey)
options.Domain = "example.com"
options.Selector = "default"
options.SignatureExpireIn = 3600
options.Headers = []string{"from", "date", "mime-version", "received", "received"}
options.AddSignatureTimestamp = true
options.Canonicalization = "relaxed/relaxed"
email.SetDkim(options)
}
// always check error before send
if email.Error != nil{
log.Fatal(email.Error)
}
// Call Send and pass the client
err = email.Send(smtpClient)
if err != nil {
log.Println(err)
} else {
log.Println("Email Sent")
}
}
Send multiple emails in same connection
//Set your smtpClient struct to keep alive connection
server.KeepAlive = true
for _, to := range []string{
"[email protected]",
"[email protected]",
"[email protected]",
} {
// New email simple html with inline and CC
email := mail.NewMSG()
email.SetFrom("From Example <[email protected]>").
AddTo(to).
SetSubject("New Go Email")
email.SetBody(mail.TextHTML, htmlBody)
// add inline
email.Attach(&mail.File{FilePath: "/path/to/image.png", Name:"Gopher.png", Inline: true})
// always check error before send
if email.Error != nil{
log.Fatal(email.Error)
}
// Call Send and pass the client
err = email.Send(smtpClient)
if err != nil {
log.Println(err)
} else {
log.Println("Email Sent")
}
}
Send with custom connection
It's possible to use a custom connection with custom dieler, like a dialer that uses a proxy server, etc...
With this, these servers params are ignored: Host, Port. You have total control of the connection.
Example using a conn for proxy:
package main
import (
"crypto/tls"
"fmt"
"log"
"net"
mail "github.com/xhit/go-simple-mail/v2"
"golang.org/x/net/proxy"
)
func main() {
server := mail.NewSMTPClient()
host := "smtp.example.com"
port := 587
proxyAddr := "proxy.server"
conn, err := getCustomConnWithProxy(proxyAddr, host, port)
if err != nil {
log.Fatal(err)
}
server.Username = "[email protected]"
server.Password = "examplepass"
server.Encryption = mail.EncryptionSTARTTLS
server.CustomConn = conn
smtpClient, err := server.Connect()
if err != nil {
log.Fatal(err)
}
email := mail.NewMSG()
err = email.SetFrom("From Example <[email protected]>").AddTo("[email protected]").Send(smtpClient)
if err != nil {
log.Fatal(err)
}
}
func getCustomConnWithProxy(proxyAddr, host string, port int) (net.Conn, error) {
dial, err := proxy.SOCKS5("tcp", proxyAddr, nil, proxy.Direct)
if err != nil {
return nil, err
}
dialer, err := dial.Dial("tcp", fmt.Sprintf("%s:%d", host, port))
if err != nil {
return nil, err
}
conf := &tls.Config{ServerName: host}
conn := tls.Client(dialer, conf)
return conn, nil
}
More examples
Golang
Golang, or Go, is a statically typed programming language developed by Google. It’s known for its simplicity, performance, and support for concurrent programming. Go is widely used in cloud computing, server-side applications, and microservices.
GitHub - goyek/goyek: Task automation Go library
gommon/color at master · labstack/gommon
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GitHub - schollz/progressbar: A really basic thread-safe progress bar for Golang applications
GitHub - free/concurrent-writer: Highly concurrent drop-in replacement for bufio.Writer
GitHub - mattn/go-colorable
GitHub - StudioSol/set: A simple Set data structure implementation in Go (Golang) using LinkedHashMap.
GitHub - essentialkaos/branca: Authenticated encrypted API tokens (IETF XChaCha20-Poly1305 AEAD) for Golang
Cloud Native Computing Foundation
GitHub - sakirsensoy/genv: Genv is a library for Go (golang) that makes it easy to read and use environment variables in your projects. It also allows environment variables to be loaded from the .env file.
GitHub - heetch/confita: Load configuration in cascade from multiple backends into a struct
GitHub - brianvoe/sjwt: Simple JWT Golang
GitHub - subpop/go-ini: Go package that encodes and decodes INI-files
GitHub - DylanMeeus/GoAudio: Go tools for audio processing & creation 🎶
GitHub - daviddengcn/go-colortext: Change the color of console text.
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GitHub - TreyBastian/colourize: An ANSI colour terminal package for Go
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GitHub - icza/session: Go session management for web servers (including support for Google App Engine - GAE).
GitHub - cristalhq/jwt: Safe, simple and fast JSON Web Tokens for Go
GitHub - lrita/cmap: a thread-safe concurrent map for go
GitHub - wzshiming/ctc: Console Text Colors - The non-invasive cross-platform terminal color library does not need to modify the Print method
GitHub - goradd/maps: map library using Go generics that offers a standard interface, go routine synchronization, and sorting
GitHub - alfiankan/teleterm: Telegram Bot Exec Terminal Command
GitHub - JeremyLoy/config: 12 factor configuration as a typesafe struct in as little as two function calls
GitHub - goraz/onion: Layer based configuration for golang
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Programming Tips & Tricks
Code smarter, not harder—insider tips and tricks for developers.
Using Lua's Garbage Collector for Fine-Tuned Memory Management in Large Applications
#1
Leveraging Lua's Environment for Dynamic Code Execution and Security
#2
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#3
Enhancing Code Readability and Debugging with Lua's Debug Library
#4
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#5
Leveraging Lua's Tail Call Optimization for Efficient Recursion and Avoiding Stack Overflow in Deep Recursive Functions
#6
Creating Custom Iterators in Lua for Traversing Complex Data Structures Like Graphs or Trees
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#8
Advanced Techniques for Asynchronous Programming in Lua Using Coroutines for High-Performance Systems
#9
Mastering Efficient Memory Management in Lua with Weak Tables for Optimal Resource Utilization
#10
Error Solutions
Turn frustration into progress—fix errors faster than ever.
Visual Studio Crashes When Opening a File or Debugging a Project
#1
Visual Studio Cannot Connect to GitHub or Other Version Control System
#2
Visual Studio Freezes During Build or Debug Process
#3
Visual Studio Fails to Build Project with "Unable to Start Program" Error
#4
Visual Studio Shows "Cannot Open the Solution" Error Message When Opening a Project
#5
Visual Studio Crashes on Startup with "The application has encountered an error" Message
#6
Visual Studio Fails to Detect Changes in Files When Using Git Integration
#7
Visual Studio Crashes with "Unknown Exception" When Trying to Build Solution
#8
Visual Studio Hangs During Debugging with "Unable to Start Program" Error
#9
Visual Studio Fails to Load Solution with "The system cannot find the file specified" Error
#10
Shortcuts
The art of speed—shortcuts to supercharge your workflow.
Maximize Your Code Navigation with Cmd + Option + Left Arrow!
#1
Feel Like a Pro with Cmd + Control + D: Quickly View Definitions Like Never Before!
#2
Unlock Speed and Precision with Cmd + Shift + M: Maximize Your Productivity!
#3
Don’t Panic, Use Cmd + Option + I to Open the Developer Tools Now!
#4
Stop Wasting Time and Jump to Your File in an Instant with Cmd + Shift + O!
#5
Quickly Fix Your Code with ‘Cmd + Option + L’ for Instant Code Formatting!
#6
Transform Your Workflow with ‘Cmd + Shift + N’ to Open a New Window in No Time!
#7
Say Goodbye to Mouse: Master ‘Cmd + Shift + F’ to Search Your Entire Codebase!
#8
Struggling to Find Files? Hit ‘Cmd + P’ and Jump Right to Your File!
#9
Never Lose Your Progress Again: Use ‘Cmd + Z’ to Undo Mistakes Instantly!
#10
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