Hi Kimberley,
ListMail would have to run on the PHP+MySQL web site, so you might have a new ListMail URL at /mail of that site. Yes, once installed you can always manually add users and send email to them. Also, you should be able to add signup forms on either site and have them point to the new ListMail installation.
When I try to log in to http:\\....mail, it comes up as 'page not found'. Why is this?
You may have heard that "index.html" is loaded by default when you browse to the "root" of a web site folder... for example the HTML for
http://example.com would be loaded from their public web folder from a file "index.html". The same can be done with PHP files with a file named index.php. When you browse to ListMail at /mail of your site, index.php is loaded (which then simply redirects to login.php). However, your new server does not support PHP scripts and therefore would not be configured to automatically load the ListMail index.php file. You could try browsing to it directly, but without PHP support the script will probably not run and may even be displayed (this can be a security issue when it comes to the config.php file).
I hope that helps.
Please let me know if you have any further questions.
Regards