HttpContext.Current returns null inside ErrorMail_Mailing handler (in Global.asax) for ELMAH

We are using ELMAH

for our application MVC asp.net

.
When any occurs, exception

ELMAH

an error message is sent that has an ErrorMail_Mailing event.I
write a handler for this event inside my Global.asax
and tries to read the value from the variable HttpContext.Current.Items

, but getting it null exception

.

Any work around please help.

I am applying what Scott suggests here: http://scottonwriting.net/sowblog/archive/2011/01/06/customizing-elmah-s-error-emails.aspx In global.asax.cs I am trying to write below event handler where I want to customize the subject line of the error message with something stored inside myHttpContext.Current.Items

  protected void ErrorMail_Mailing(object sender, Elmah.ErrorMailEventArgs e)
        {               
            if (HttpContext.Current.Items["CustomerName"] != null)
            {
                e.Mail.Subject = "Error came to / " + HttpContext.Current.Items["CustomerName"] + " / Error Type: " +
                                 e.Error.Type;
            }
        }