I'm trying to create a mail server, but I'm not able to connect to my DO droplet's domain, which I need to do to get a Let's Encrypt SSL certificate. It refuses conection. letsdebug.net says:
[My domain name] has an A (IPv4) record ([my droplet's IP address)) but a request to this address over port 80 did not succeed. Your web server must have at least one working IPv4 or IPv6 address.
71ms: Experienced error: dial tcp [my droplet's IP]:80: connect: connection refused
So, I decided to try running
sudo netstat -nlp which outputted the following:
Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:33060 0.0.0.0:* LISTEN 2882/mysqld tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 2882/mysqld tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 493/systemd-resolve tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 768/sshd: /usr/sbin tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 146987/master tcp6 0 0 :::22 :::* LISTEN 768/sshd: /usr/sbin tcp6 0 0 :::25 :::* LISTEN 146987/master udp 0 0 127.0.0.53:53 0.0.0.0:* 493/systemd-resolve raw6 0 0 :::58 :::* 7 490/systemd-network raw6 0 0 :::58 :::* 7 490/systemd-network
And there is clearly nothing listening on port 80. How do I get something to listen to it? Do I need to install Nginx or something - namely set up a webserver? Why would I need to do that? Does this mean I need a web server built to install a mail server? I'm a complete novice when it comes to this stuff.
I am being told that it is only required for a Let's Encrypt certificate. In this tutorial,
dovecot.pem is used for both the cert and key file. Will this suffice instead if I'm using Dovecot?
Update: no IP address found for my subdomain
On Michael Hampton's advice, I tried
sudo certbot certonly --standalone -d mail.example.com putting in my own mail subdomain and have seemed to have opened another can of worms:
Detail: No valid IP addresses found for [my mail subdomain]
This is a bit confusing. Perhaps I have set my MX record wrong? I will list out my DNS records (I've blacked out my droplet's IP address and domain name as I have no clue if it is safe or not to share these things over the internet. If they are necessary to include and it's safe I have no problem unredacting this):
Here, the redacted bits in the 'Value' column all hide by droplet's IP address and the redacted bits in hostname hide my domain url.