Thank you for your feedback!

We are sorry that you are dissatisfied with our service.
On the product's website you have the choice between mail.com MailCheck for Firefox with or without the preset new tab page by selecting the correct button.
If you install the mail.com MailCheck right here from the Firefox Add-Ons Store, the new tab isn't changed to our site.

Regarding the permissions, you can find an help article here: https://support.mail.com/mailcheck/firefox/permissions.html
This article explains, why you are asked for so many permissions to use MailCheck. Part of the explanation is that Firefox enlists all permissions, even if they are optional and only asked for in case the user enables the corresponding feature or accesses the specific website with MailCheck.

We would be very happy, if you tried out the MailCheck version here from the Mozilla Firefox Add-ons Store and maybe even reconsidered your rating.

Kind regards,
Your MailCheck-Team