If you use Apache server then …
In the httpd.conf file, or in the include file containing the VirtualHost section for your web account, add a line like this (if it is not already present):
ServerAlias *.example.com
Also create a wildcard DNS record like:
*.example.com A 192.0.43.10
REF https://codex.www.ads-software.com/Configuring_Wildcard_Subdomains.
