If your DNS record points to your server IP that's all it needs from the DNS perspective. Now, your server needs to map those requests to your WordPress website. That's handled by Apache or Nginx, or whatever other server you may be using.
It's good to see Roundcube found a new home, which means development will pickup and more features are coming ๐
Do you use Roundcube? I do ๐
https://nextcloud.com/blog/open-source-email-pioneer-roundcube-comes-aboard-nextcloud/
FreeScout.net is a great, free, and open source option. Takes its inspiration from HelpScout.
If your DNS record points to your server IP that's all it needs from the DNS perspective. Now, your server needs to map those requests to your WordPress website. That's handled by Apache or Nginx, or whatever other server you may be using.