title: Does not match a verified sender Identity error in golang
body: <p>I'm working on sent emails when a user will do signup. I'm using new SendGrid account for free but while I'm running my function then it will show me the below error can anyone tell me how I' will resolve it. Below is my Golang function</p>
  
  <pre><code>func SendOtpMail(OTP string) (err error) {
      from := mail.NewEmail("Test", "test@example.com")
      subject := "Comfirmation Mail"
      to := mail.NewEmail("puneet", "puneet123@gmail.com")
      // plainTextContent := ""
      htmlContent := "Your confirmation OTP is = " + OTP
      message := mail.NewSingleEmail(from, subject, to, " ", htmlContent) // ("" = plainTextContent)
      client := sendgrid.NewSendClient("Api_key")
      response, err := client.Send(message)
      fmt.Println(response)
      fmt.Println(err)
      return err
  }
  </code></pre>
  
  <p>In response, it will return me the below-console output:</p>
  
  <pre><code>&amp;{403 {"errors":[{"message":"The from address does not match a verified Sender Identity. Mail cannot be sent until this error is resolved. Visit https://sendgrid.com/docs/for-developers/sending-email/sender-identity/ to see the Sender Identity requirements","field":"from","help":null}]} map[Access-Control-Allow-Headers:[Authorization, Content-Type, On-behalf-of, x-sg-elas-acl] Access-Control-Allow-Methods:[POST] Access-Control-Allow-Origin:[https://sendgrid.api-docs.io] Access-Control-Max-Age:[600] Connection:[keep-alive] Content-Length:[281] Content-Type:[application/json] Date:[Sat, 25 Apr 2020 12:56:25 GMT] Server:[nginx] X-No-Cors-Reason:[https://sendgrid.com/docs/Classroom/Basics/API/cors.html]]}
  </code></pre>
  
  <p></p>
  
  <p>I also implemented this same in 2019 then it is working but now I want to change it then this is showing me this error. Please help me out with this.</p>