This is the 22nd day of my participation in Gwen Challenge

Use GOLANG to send emails

Let’s review the captcha case of GO we talked about last time

  • Verification code type sorting
  • Installation of the verification code library
  • Verification code library source code introduction
  • Practical operation, coding
  • Verification code effect display

Want to see how GO do captcha, welcome to see the article GO captcha case

In life and work, we are inseparable from the sending and receiving of emails, or check and send on the mobile phone, or in front of their own computer for email editing and processing

However, we will find that most of the time, we have to send a certain type of mail at the same time every day, and the content is similar.

And, sometimes because of a variety of reasons, can not send the mail on time, at this time, if we can write a customized mail program that can be said to be very fragrant

So, let’s start with some common sense

What’s the mail?

Mail is a document processed by means of transfer

The process by which mail is delivered is called post, and the organization or system that provides mail services is called post

There are two types of mail: domestic mail and international mail

So what is E-mail?

E-mail is a form of communication that provides the exchange of information electronically. It is the most widely used service on the Internet

What are the advantages of email?

E-mail The web-based E-mail system has the following advantages:

  • The price is very low

No matter where you send it, you only have to pay for the Internet

  • Transport fast

Within seconds, it can be sent to any designated destination in the world, connecting with web users anywhere in the world

What is the format of E-mail?

  • The text
  • image
  • Voice etc.

Think about the steps you need to go through every time you send an email

  • Open the computer
  • Enter the browser
  • Open email
  • New-edit-Send

Most of it is copy-pasted,

GOLang is a great tool to use to send emails

E-mail protocol

When we use programming language, we need to follow the programming language specification, and when we browse the web in the browser, we need to follow various network protocols

Well, we email senders must also know what email protocols are available. Let’s list them

  • SMTP

SMTP is a simple mail transfer protocol. It is a set of specifications used to transfer mails from source addresses to destination addresses. It controls the mail transfer mode

In addition, SMTP belongs to TCP/IP protocol cluster

  • POP3

Version 3 of the Post Office Protocol, the first offline protocol standard for Internet E-mail

  • IMAP

Is a new protocol that is superior to POP

Like POP, IMAP can download messages, delete messages from the server, or ask if there are new messages

IMAP allows users to create and manage mail folders or mailboxes, delete messages, and query some or all of the contents of a letter on the server

All of this can be done without the need to download mail from the server to the user’s PC

OK, let’s start coding

Start coding emails

Let’s use SMTP protocol to send mail today, there are several steps

  • Above QQ mailbox, get authorization code
  • Code and installemailMail library
  • Start sending emails

inQQFrom the mailbox. Get the authorization code

  • Enter theQQEmail, clickSettings -> Account

  • Down the page, see the POP3 / IMAP/SMTP/Exchange/CardDAV/CalDAV service

  • openPOP3/SMTPservice
  • openIMAP/SMTPservice
  • Generate the authorization code, the authorization code itself to find a place to save

Code and installemailMail library

Let’s write this mail small case, use GO package is “github.com/jordan-wright/email”, we can manually install

 go get github.com/jordan-wright/email
Copy the code

No manual installation is also no problem, we can now look at writing a first version of the small case of sending mail

package main

import (
   "github.com/jordan-wright/email"
   "log"
   "net/smtp"
)

func main(a) {
   // Simply set the log parameter
   log.SetFlags(log.Lshortfile | log.LstdFlags)

   em := email.NewEmail()
   // Set sender's email address
   em.From = "xx <[email protected]>"
    
   // Set receiver's email address // Set receiver's email address
   em.To = []string{"[email protected]"}
    
   // Set the theme
   em.Subject = "The little devil boy sent you an E-mail."
    
   // Simply set the content of the file to be sent, temporarily set to plain text
   em.Text = []byte("Hello world, let's use Golang to send an email!!")
    
   // Set the server configuration
   err := e.Send("smtp.qq.com:25", smtp.PlainAuth(""."My own email account"."Authorization code for your email address"."smtp.qq.com"))
   iferr ! =nil {
      log.Fatal(err)
   }
   log.Println("send successfully ... ")}Copy the code

The effect of running the above code is as follows:

2021/06/xx xx:36:28 main.go:28: send successfully ...
Copy the code

Let’s have a look at our mailbox

Sure enough, it was a success

So that’s it for today’s article sharing, when you ask, I want to post, I want to posthtmlContent, I want to send attachments, I even want to secretly cc some people

Good arrangement

sendHTMLContent + Attachment

Let’s take a look at which fields the library supports. The NewEmail method above returns a pointer

// NewEmail creates an Email, and returns the pointer to it.
func NewEmail(a) *Email {
   return &Email{Headers: textproto.MIMEHeader{}}
}
Copy the code

This pointer points to a mail data structure. Let’s take a look

// Email is the type used for email messages
type Email struct {
   ReplyTo     []string    
   From        string		/ / the sender
   To          []string		/ / the recipient
   Bcc         []string		/ / send
   Cc          []string		/ / cc
   Subject     string		/ / theme
   Text        []byte // Plaintext message (optional)  
   HTML        []byte // Html message (optional)
   Sender      string // override From as SMTP envelope sender (optional)
   Headers     textproto.MIMEHeader  / / agreement
   Attachments []*Attachment    / / accessories
   ReadReceipt []string
}
Copy the code

Look at the above structure, we can send mail, cc, BCC, add attachments, or send HTML content, let’s change the above code

func main(a) {
   // simply set the l og parameter
   log.SetFlags(log.Lshortfile | log.LstdFlags)

   em := email.NewEmail()
   // Set the sender's mailbox
   em.From = "xx <[email protected]>"
   // Set the recipient's mailbox
   em.To = []string{"[email protected]"}

   / / cc
   em.Cc = []string{"[email protected]"}

   / / send
   em.Bcc = []string{"[email protected]"}

   // Set the theme
   em.Subject = "The little devil boy sent you an E-mail."
   // Set the content of the file to be sent
   em.HTML = []byte(` < h3 > < a href = "https://juejin.cn/user/3465271329953806" > welcome to small familiars which zha home page < / a > < / h3 > < br / > < table border = "0" Style =" max-width: 100%; clear: both; min-height: 1em; Cellpadding = "3 px" > < tr > < td > 1 < / td > < td > < a href = "https://juejin.cn/post/6975686540601245709" > GO defer implementation principle in < / a > < / td > < / tr > < tr > < td > 2 < / td > < td > < a href = "https://juejin.cn/post/6975280009082568740" > GO in Chan principle share < / a > < / td > < / tr > < tr > 3 < / td > < td > < td > < a href = "https://juejin.cn/post/6974908615232585764" > GO map in the implementation of the principle of < / a > < / td > < / tr > < tr > < td > 4 < / td > < td > < a href = "https://juejin.cn/post/6974539862800072718" > GO slice in the implementation of the principle of < / a > < / td > < / tr > < tr > < td > 5 < / td > < td > < a Href = "https://juejin.cn/post/6974169270624190495" > GO string in the implementation of the principle of < / a > < / td > < / tr > < tr > < td > 6 < / td > < td > < a Href = "https://juejin.cn/post/6973793593987170317" > GO ETCD coding in case share < / a > < / td > < / tr > < tr > < td > 7 < / td > < td > < a Href = "https://juejin.cn/post/6973455825905909797" > service registration and discovery of ETCD < / a > < / td > < / tr > < tr > < td > 8 < / td > < td > < a Href = "https://juejin.cn/post/6973108979777929230" > GO channel, and sharing of sync bag < / a > < / td > < / tr > < tr > < td > 9 < / td > < td > < a Href = "https://juejin.cn/post/6972846349968474142" > GO lock and atomic operation share < / a > < / td > < / tr > < / table > `)
   // Add attachments
   em.AttachFile("./test.html")
   // Set the server configuration
   err := e.Send("smtp.qq.com:25", smtp.PlainAuth(""."My own email account"."Authorization code for your email address"."smtp.qq.com"))
   iferr ! =nil {
      log.Fatal(err)
   }
   log.Println("send successfully ... ")}Copy the code

Once it’s up and running, let’s check email

Cc, BCC, add attachments, send HTML content, all on top

How can I improve the performance of sending emails

The get github.com/jordan-wright/email package provides a connection pool for us, which you can say is not sweet, we can reuse the last network connection to send email, rather than each time we send email, establish a connection

We all know that building connections takes time and resources, so we need to optimize as much as possible

In another DEMO, connection pooling, let’s use connection pooling to create a channel with five buffers, and let three coroutines go to the channel to fetch data and send emails

func main(a) {

   // simply set the l og parameter
   log.SetFlags(log.Lshortfile | log.LstdFlags)

   // Create a channel with 5 buffers and the data type is * email.email
   ch := make(chan *email.Email, 5)
   / / the connection pool
   p, err := email.NewPool(
      "smtp.qq.com:25".3.// Set the number to 3
      smtp.PlainAuth(""."My own email"."Authorization code for your email address"."smtp.qq.com"),iferr ! =nil {
      log.Fatal("email.NewPool error : ", err)
   }
	
   // sync package to control synchronization
   var wg sync.WaitGroup
   wg.Add(3)
   for i := 0; i < 3; i++ {
      go func(a) {
         defer wg.Done()
          // If ch has no data, block; if ch is closed, exit the loop
         for e := range ch {
            // The timeout is 10 seconds
            err := p.Send(e, 10*time.Second)
            iferr ! =nil {
               log.Printf( "p.Send error : %v , e = %v , i = %d\n", err , e, i)
            }
         }
      }()
   }

   for i := 0; i < 5; i++ {
      e := email.NewEmail()
      // Set the basic information for sending emails
      e.From = "xx <[email protected]>"
      e.To = []string{"[email protected]"}
      e.Subject = "test email.NewPool " + fmt.Sprintf(" the %d email",i)
      e.Text = []byte(fmt.Sprintf("test email.NewPool , the %d email !", i))
      ch <- e
   }

   // Close the channel
   close(ch)
   // Wait for the subcoroutine to exit
   wg.Wait()
   log.Println("send successfully ... ")}Copy the code

After running the above code, let’s check the mailbox

As you can see, the emails are not sent in order, that’s right

If you have any questions about using Sync above, please check out the GO channel and sync package sharing article

conclusion

  • Shared email. What is email
  • What are the mail protocols
  • How do I use GOLANG to send email
  • How to send an email with plain text,HTMLContents, attachments, etc
  • How to cc or BCC an email
  • How can I improve the performance of sending emails

GOLANG how to send email (QQ mailbox) | Go theme month

Welcome to like, follow and favorites

Friends, your support and encouragement, I insist on sharing, improve the quality of the power

Well, that’s it for now, and next time share a wave of GO crawlers

Technology is open, our mentality, should be more open. Embrace change, live in the sun, and strive to move forward.

I am Nezha, welcome to like, see you next time ~