map $http_upgrade $proxy_connection {
  default upgrade;
  "" close;
}

server {
    listen 443 ssl;
    server_name mail.grenu4.ru;

    ssl_certificate /etc/letsencrypt/live/mail.grenu4.ru/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/mail.grenu4.ru/privkey.pem;

    access_log /var/log/nginx/mail.grenu4.ru_access.log main;
    error_log /var/log/nginx/mail.grenu4.ru_error.log notice;

    location / {
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_pass http://127.0.0.1:8087;

        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $proxy_connection;
    }

    location = /robots.txt {
        add_header Content-Type text/plain;
        return 200 "User-agent: *\nDisallow: /\n";
    }
}