Send email from Go over SMTP

Go's net/smtp client can STARTTLS to Unitpost on port 587. Username is the literal `unitpost`; password is an API key.

1. 1

   Send with net/smtp

   Go

   package main
   
   import (
       "crypto/tls"
       "net/smtp"
       "os"
   )
   
   func main() {
       host := "smtp.unitpost.com"
       auth := smtp.PlainAuth("", "unitpost", os.Getenv("UNITPOST_API_KEY"), host)
       to := []string{"customer@example.com"}
       msg := []byte("From: you@yourdomain.com\r\n" +
           "To: customer@example.com\r\n" +
           "Subject: Hello from Go\r\n" +
           "\r\n" +
           "Sent via SMTP.\r\n")
   
       c, err := smtp.Dial(host + ":587")
       if err != nil {
           panic(err)
       }
       defer c.Close()
       if err = c.StartTLS(&tls.Config{ServerName: host}); err != nil {
           panic(err)
       }
       if err = c.Auth(auth); err != nil {
           panic(err)
       }
       if err = c.Mail("you@yourdomain.com"); err != nil {
           panic(err)
       }
       if err = c.Rcpt(to[0]); err != nil {
           panic(err)
       }
       w, err := c.Data()
       if err != nil {
           panic(err)
       }
       if _, err = w.Write(msg); err != nil {
           panic(err)
       }
       if err = w.Close(); err != nil {
           panic(err)
       }
       _ = c.Quit()
   }

   Port 587 needs an explicit STARTTLS before AUTH (PLAIN and LOGIN are both accepted). From must be on a verified domain.

2. 2

   Verify delivery

   The message appears in Activity.