Webmail/domain is unavailable: Server not found

Symptoms

• When opening webmail/domain in a browser, it returns one of the following errors:

  • Firefox:

    "Server not found. Firefox can't find the server at webmail.example.com"

  • IE:

    "Internet Explorer cannot display the webpage"

  • Chrome:

    "Oops! Google Chrome could not find webmail.example.com"

    OR

    "ERR_NAME_NOT_RESOLVED"

    OR

    "404 not found"

• Let's Encrypt cannot be issued on the domain:

  Error: Could not issue a Let's Encrypt SSL/TLS certificate for example.com. Authorization for the domain failed.
  <...>
  Details:
  Type: urn:acme:error:connection
  Status: 400
  Detail: Fetching http://example.com/.well-known/acme-challenge/cCMl-4ZDqnWT-DEADBEEFl0sl_z9KVN_Ghkc1f1pMpQ: Timeout during connect (likely firewall problem)

Cause

Webmail/domain does not resolve correctly in global DNS system because Plesk server is not set up to manage DNS.

Resolution

To verify the root cause, run the following commands in a command-line interface:

Note: the commands are identical on Windows, Linux and MacOS. The commands below are valid for webmail as well

1. First, test if domain can be resolved to an IP address in general:

   C:> nslookup example.com
   Server: mydns.server.com
   Address: 203.0.113.2

   Non-authoritative answer:
   Name: example.com
   Address: 203.0.115.20

   Output explanation:

   • Server and Address represent hostname and address of the server that provides response for the query sent by command nslookup;
   • Name and Address(es) are the domain name which IP address is being queried and the IP address that was provided by the server as a response.

   However, if the following output is seen instead, it means that the domain does not resolve properly:

   C:> nslookup webmail.example.com
   Server: mydns.server.com
   Address: 203.0.113.2

   *** UnKnown can't find example.com: No response from server

2. Next, check if DNS service on the server with Plesk contains proper record for the domain:

   C:> nslookup webmail.example.com 203.0.115.20 <---- IP address of the server with Plesk
   Server: UnKnown
   Address: 203.0.115.20

   Name: webmail.example.com
   Address: 203.0.115.20

If the first command does not return anything or returns a wrong IP address, and the second command returns valid records, then Plesk server is not serving the DNS zone for a domain.

There are two options to resolve the issue:

• Set Plesk server to be nameserver of the domain: How to use DNS with a Plesk server;

• Add a respective A-record on a registrar/3rd-party DNS side.

Note: a similar issue can be observed for other DNS records like TXT, MX, CNAME and etc.