Thanks everyone for your comments, please consider the following.
Here is a comparison between Nutsmail and HordeSkinsPlus.
Nutsmail from what we can see offers individual skins, they have 11 skins plus Squirrelmail webmail and pre-configured plugins at $372 for all 11 or for $199 you can buy all of them in one shot. Their installation instructions give you a default setup for one domain. if you want a more advanced server-wide installation your on your own or you can order one from them, it's extra $$$. There is no auto installer, it is a different setup from Horde so you will have to install the product yourself. You can more than likely find help in the Plesk forums from more advanced users, you'll have to do some research or simply pay the extra. If you pay the extra it will not help you customize each domain once the product is installed, your on your own for that.
Nutsmail/Squirrelmail can not be modified through the Plesk control panel, you can not customize each domain on an individual bases through Plesk with simple point and click functionality, you can not customize all of a clients domains together simultaneously, you cannot add and remove webmail applications on a per domain bases through the Plesk control panel. . you will never have the branding options that HordeSkinsPlus offers you through the Plesk control panel and you are still left with 2 different interfaces that your clients have to use.
HordeSkinsPlus has 16 skins, an add-on management module for Plesk and an auto installer that will setup the product server wide for you, it creates a backup of Horde and includes an uninstaller that will set Horde back to the original configuration you had before installing the product. Once the product is installed you can customize every domain with point and click ease through the Plesk control panel.
HordeSkinsPlus gives you and your clients an interface that is identical to your control panel offering. It allows you to brand each domain, it allows you to simultaneously brand every domain owned by individual clients/resellers. It allows you to setup your own login/logout pages that you have completely customized anywhere you want and we will be adding to this to give you even more choices, samples and code you can use with point and click ease all through the Plesk control panel.
The features in our product are unique there are no other webmail products you can buy that integrate point and click management functionality for webmail into the Plesk control panel. We have not over written the default horde skins they are still available to use for any domain you choose to use them for, this means you can charge a setup fee or a premium price for customers that want to use the Plesk theme, or you can use the Plesk theme server wide, we've given you the tools to generate extra revenue if you wish and we will be continually adding applications and functionality to the product. We want you to generate many times your investment while providing significant value for your clients. The product will reduce your technical support requirements.
We have given you a way to save time, installing and setting up our product literally takes less than 5 minutes, customizing an individual domain takes on average less than a minute, customizing and branding all of the domains owned by an individual client simultaneously takes on average less than a minute. We have no branding or copyright footers anywhere that your clients will see other than a default sample logo that you can replace.
We have a development path for this product which means all of our clients have some input into what features they would like to see in the coming releases, and we want to give you all the features that are important to you. All of our customers will receive free upgrades with the new features they want.
As you must know professional software requires professional support. Our investment has been and continues to be substantial as is the value our clients are receiving in quality product and world class support.
Please keep posting your comments, we appreciate them very much and we will continue to monitor this thread.
Thanks again everyone.