Expected response code "250" but got an empty response

I can send my emails in localhost!I get this error

Expected response code "250" but got an empty response.

I don't understand how update .env

# .env# .MAILER_DSN isn't a real address: it's a simple format that offloads most of the configuration work to mailer.MAILER_DSN=sendgrid://KEY@default

works in localhost but not in the hosting site.

I use Symfony 4.4.