GMX.com MailCheck

With the GMX.com MailCheck extension, you only need to log in once with your GMX.com-credentials in order to gain quick and simplified access to your inbox. From then on, you merely click on the envelope icon in your browser for instant access to all of your emails (e.g. gmx.com, mail.com, Outlook Live). No more searching for your email provider in a search engine then directing toward the sign-in page, and finally entering your login details—skip all of this with easy one-click login with MailCheck from GMX.com.

Enable optionally the mail preview panel in MailCheck.
Delete unread mails directly from your inbox.
Access your inbox for writing new mails.