Make README clearer about PTR record

README.md

@@ -51,9 +51,10 @@ actually works perfectly.
    **CNAME record** for your `mail.` subdomain.
 4. **A Reverse DNS entry for your site.** Go to your VPS settings and add an
    entry for your IPV4 Reverse DNS that goes from your IP address to
-   `mail.<yourdomain.com>`. If you would like IPV6, you can do the same for
-   that. This has been tested on Vultr, and all decent VPS hosts will have
-   a section on their instance settings page to add a reverse DNS PTR entry.
+   `<yourdomain.com>` (not mail subdomain). If you would like IPV6, you can do 
+   the same for that. This has been tested on Vultr, and all decent VPS hosts
+   will have a section on their instance settings page to add a reverse DNS PTR 
+   entry.
    You can use the 'Test Email Server' or ':smtp' tool on
    [mxtoolbox](https://mxtoolbox.com/SuperTool.aspx) to test if you set up
    a reverse DNS correctly. This step is not required for everyone, but some