Do you have to use FTP or do you have other method of access to the storage volume?
If you have like SSH access for example, you could potentially mount the storage volume over SSH (SSHFS) - it would then be basically seen by Plesk as just being local storage.
Sounds like you're going from a network firewall, to a server level firewall. They can work in tandem if you want.
I would close what ports are not needed within the Plesk Firewall, before disabling the old one.
Windows ain't exactly my cup of tea but a few things that came to mine;
- Service is started ; Start, Run, services.msc
- Configured in IIS? Set up SmarterMail as an IIS Site (IIS 7.0/7.5) - SmarterTools
A bulk of your user's data is going to be in vhosts. I would recommend just leaving the 30GB as is, and then move the vhosts directory to the new 300GB partition by using the transvhosts utility...
Do you have port 21 open on your firewall?
If using Passive FTP, you'll also want to make sure the range listed at Tools & Settings > FTP Settings > Port or port range for passive FTP mode connections - is also open.
Do you need to actually move the entire var?
For example, you can move just the vhosts location by using the transvhosts utility;
https://support.plesk.com/hc/en-us/articles/12377953257111--How-to-change-virtual-hosts-location-in-Plesk-for-Linux-
Have you tried testing the email using mail tester?
https://www.mail-tester.com/
Should point out any recommendations as far as what to change to maximize delivery.
Correct, this. A username for email, even when configuring a mail client such as Outlook is GENERALLY going to be the full email address in most cases.
I'm assuming at this other host you have either a VPS or Dedicated, and that they are bundling it in as part of that service. There's a nice price break for example for a larger datacenter or host that purchases an excessive number of licenses at which point per license costs aren't that bad and...
You do need to retain a license to even use the various Plesk command line tools as well even if you're not logging in to the UI.
I think that's about $21 USD which is a bit high for the web admin edition. You could get it directly from Plesk for about $13 if you were looking to save a few bucks.
Another option instead of changing the URL in the database would be to just temporarily add the preview URL to your wp-config.php file from the file manager which can be done in the following form;
define( 'WP_HOME', 'http://yourpreviewurl.com' );
define( 'WP_SITEURL'...
Generally, testing can be done by modifying what is called the host file on your local system to point to the new IP address. This allows you to test it with the actual domain prior to updating the actual DNS affecting everybody.
The following explains it better...