Beispiel für Massenmailer

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package main

import (
    "fmt"
    ht "html/template"
    "log"
    "math/rand"
    "os"
    tt "text/template"
    "time"

    "github.com/wneessen/go-mail"
)

// User is a simple type allowing us to set a firstname, lastname and mail address
type User struct {
    Firstname string
    Lastname  string
    EmailAddr string
}

// Our sender information that will be used in the FROM address field
const (
    senderName = "ACME Inc."
    senderAddr = "noreply@acme.com"
)

const (
    textBodyTemplate = `Hi {{.Firstname}},

we are writing your to let you know that this week we have an amazing offer for you.
Using the coupon code "GOMAIL" you will get a 20% discount on all our products in our
online shop.

Check out our latest offer on https://acme.com and use your discount code today!

Your marketing team
  at ACME Inc.`

    htmlBodyTemplate = `<p>Hi {{.Firstname}},</p>
<p>we are writing your to let you know that this week we have an amazing offer for you.
Using the coupon code "<strong>GOMAIL</strong>" you will get a 20% discount on all 
our products in our online shop.</p>
<p>Check out our latest offer on <a href="https://acme.com" target="_blank">https://acme.com</a>
and use your discount code today!</p>
<p>Your marketing team<br />
&nbsp;&nbsp;at ACME Inc.</p>`
)

func main() {
    // Define a list of users we want to mail to
    ul := []User{
        {"Toni", "Tester", "toni.tester@example.com"},
        {"Tina", "Tester", "tina.tester@example.com"},
        {"John", "Doe", "john.doe@example.com"},
    }

    // Prepare the different templates
    ttpl, err := tt.New("texttpl").Parse(textBodyTemplate)
    if err != nil {
        log.Fatalf("failed to parse text template: %s", err)
    }
    htpl, err := ht.New("htmltpl").Parse(htmlBodyTemplate)
    if err != nil {
        log.Fatalf("failed to parse text template: %s", err)
    }

    var ms []*mail.Msg
    r := rand.New(rand.NewSource(time.Now().UnixNano()))
    for _, u := range ul {
        rn := r.Int31()
        m := mail.NewMsg()
        if err := m.EnvelopeFrom(fmt.Sprintf("noreply+%d@acme.com", rn)); err != nil {
            log.Fatalf("failed to set ENVELOPE FROM address: %s", err)
        }
        if err := m.FromFormat(senderName, senderAddr); err != nil {
            log.Fatalf("failed to set formatted FROM address: %s", err)
        }
        if err := m.AddToFormat(fmt.Sprintf("%s %s", u.Firstname, u.Lastname), u.EmailAddr); err != nil {
            log.Fatalf("failed to set formatted TO address: %s", err)
        }
        m.SetMessageID()
        m.SetDate()
        m.SetBulk()
        m.Subject(fmt.Sprintf("%s, we have a great offer for you!", u.Firstname))
        if err := m.SetBodyHTMLTemplate(htpl, u); err != nil {
            log.Fatalf("failed to set HTML template as HTML body: %s", err)
        }
        if err := m.AddAlternativeTextTemplate(ttpl, u); err != nil {
            log.Fatalf("failed to set text template as alternative body: %s", err)
        }

        ms = append(ms, m)
    }

    // Deliver the mails via SMTP
    c, err := mail.NewClient("smtp.example.com",
        mail.WithSMTPAuth(mail.SMTPAuthPlain), mail.WithTLSPortPolicy(mail.TLSMandatory),
        mail.WithUsername(os.Getenv("SMTP_USER")), mail.WithPassword(os.Getenv("SMTP_PASS")),
    )
    if err := c.DialAndSend(ms...); err != nil {
        log.Fatalf("failed to deliver mail: %s", err)
    }
    log.Printf("Bulk mailing successfully delivered.")
}
}
}
}