Enqueue Task SendEmail generate multiple emails

environment :
dotnet --info
SDK de .NET (que refleje cualquier global.json):
Version: 6.0.200
Commit: 4c30de7899

Entorno de tiempo de ejecución:
OS Name: debian
OS Version:
OS Platform: Linux
RID: debian-x64
Base Path: /usr/share/dotnet/sdk/6.0.200/

Code :
`public IActionResult Index()
{
Hangfire.BackgroundJob.Enqueue(() => SendMail());
return View();
}

public void SendMail()
{
using (var _message = new MailMessage())
{
_message.From = new MailAddress("user@server.net");
_message.To.Add("user@mail.cl");

_message.Subject = "Test Mail";
_message.Body = "Test Mail";
_message.IsBodyHtml = true;

using (var smtpClient = new SmtpClient("mail.server.net"))
{
smtpClient.Port = 587;
smtpClient.EnableSsl = true;
smtpClient.Credentials = new NetworkCredential("usermail", "passmail");
smtpClient.Send(_message);
Console.WriteLine("Send Test Mail");
}
}
}`

result :

more than 18 were received Email, only one execution Index

Start by reproducing the report with the Index action enqueueing SendMail and check whether one invocation results in multiple email deliveries. Investigate the enqueue and execution behavior around these entry points; done means a single execution sends only one email, or the cause and required configuration are clearly documented.

Written by the indexing model from the issue text.