Xobni has long been a popular plug-in for email users who rely heavily on Outlook – and recommended by us on a previous occasion. Once installed, it appears as a collapsible sidebar on the right of your inbox and adds a handful of features that will make email more searchable and social. Being offered as a free download, Xobni is definitely worth a try if not for its speedy searches and Gmail-like threaded conversations alone; but would you actually pay for more advanced features?

The company behind this tool certainly hopes so. Month after receiving $7 million in financing, they’ve announced a premium version of the software that adds extra features like the ability to fine-tune searches using a GUI-based query builder, search through calendar appointments and tasks, and see Xobni’s automatic suggestions when you’re typing the names of email recipients. Searching full text within conversations and networks is another useful feature that takes life in Xobni Plus. You can see a full feature comparison here.

This collection of small but useful updates is available for a one-time fee of $29.99 – and $9.95 for each additional computer. Xobni Plus provides one-year of technical support, an ad-free environment, and is the first of several revenue sources the company hopes to draw from in the future.