Email works on my Linode, but my website is down

If you're able to send email and access your Plesk server, but your site is not resolving, it sounds like you may need to adjust your firewall rules or the configuration of your webserver.

You can use a tool like nmap to test port status, and probe which services are running on them:

nmap -p 25,465,587,80,443,8443 <IP Address Here>

Starting Nmap 6.47 ( http://nmap.org ) at 2018-03-16 13:32 EDT
Nmap scan report for example.members.linode.com (123.45.67.89)
Host is up (0.25s latency).

PORT     STATE  SERVICE
25/tcp   open   smtp
80/tcp   closed http
443/tcp  closed https
465/tcp  open   smtps
587/tcp  closed submission
8443/tcp open   https-alt

In this case, SMTP and SMTPS are open and listening for connections, and Plesk's standard 8443 port is open, but HTTP and HTTPS are closed. When nmap shows a port as closed, it could mean that your operating system's firewall is blocking communication on that port, or it could mean that no service is currently configured to listen for connections on that port.

I would suggest first reviewing your webserver's configuration to make sure it is set up to listen for connections on ports 80 and 443. The location of your configuration file will vary depending on the specific server you are using, such as Apache or Nginx.

If you are still unable to reach your site, you should review your firewall rules to make sure you are not blocking these ports. In Ubuntu, you can check iptables rules with the following command:

sudo iptables -L