I'm using Mailkit to send mails in my .Net Core 5 mvc application. In Visual Studio everything works fine when debugging. I receive the mails i send so i know the settings are correct. But when i publish the application to IIS, i'm no longer receiving the mail.

In my logging, everything looks fine. I'm getting that the message got sent.I'm using ovh to send the mail with these settings

try
{    
  await client.ConnectAsync("ssl0.ovh.net", 587, SecureSocketOptions.StartTls);
  await client.AuthenticateAsync("myEmailadress", "myPassword");
  await client.SendAsync(message);
  await client.DisconnectAsync(true);
  _log.savelog("success");
}
catch(exception ex)
{
  _log.savelog("error");
}

The above settings work in Visual Studio when debugging. The log says "success". After publishing, no mail is received while the log says "success" I have no idea where to look for the problem

EDIT: because i didn't find a solution, i registered for a free account at SendGrid. Tested everything and received email. But when i publish the appliction I don't receive the mails. Now i'm completly lost