Currently, Senders is only available for Gmail and Google Apps accounts. We are working hard to add other providers such as Yahoo! Mail and Outlook.com. We are also designing support for hosted Exchange servers. If you join our mailing list by entering your email address on the sign-up page, we will notify you as soon as we’ve added support for other email providers.
In terms of email client compatibility, because we add the Senders Card to your email messages, Senders is compatible with all devices, systems, and apps, including the Outlook app configured with a Google account.