Microsoft will charge users $35 per user per month, or $420 per year, for its new highest-end Office 365 business plan.

Microsoft officials went public with the pricing for Office 365 E5, its top-of-the-line commercial Office 365 offering, on November 30 during the company's Convergence EMEA conference. Office 365 E5 is available to customers for purchase starting tomorrow, December 1.

Office 365 E4 -- the current high-end version of Microsoft's Office 365 line -- sells for $22 per user per month, or $264 per user, per year.

The Office 365 E5 SKU will include Skype for Business (Lync) with support for features including Cloud PBX and Meeting Broadcast; new analytics features, like Power BI Pro and Delve Organizational Analytics; and new advanced security features, such as eDiscovery, Customer Lockbox, and Safe Attachments.

Office 365 E4 includes Skype for Business with Enterprise Voice and unified messaging; the full suite of locally downloadable Office apps; and Power BI for Office 365 (which is being superseded by Power BI pro).

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Microsoft is planning to retire E4 and replace it with E5. However, Office 365 E4 will remain on the price list till June 30, 2016, Microsoft officials have said.

The E1 and E3 versions of Office 365 will retain their current prices of $8 per user per month, and $20 per user per month, respectively.

Office 365 E1 users will get new work-management capabilities, as well as Skype for Business's Meeting Broadcast functionality added to their plans for no additional charge. Office 365 E3 users will get those same two new features, as well as the option to purchase Equivio Analytics for eDiscovery. (Microsoft bought Equivio in January 2015.)

Skype Meeting Broadcast enables users to broadcast of a Skype for Business meeting on the Internet to up to 10,000 people, who can attend in a browser.

Office 365 E5 users get all the features that E1 and E3 users get, plus other analytics and networking functionality, including Cloud PBX and PSTN Conferencing.

The Skype for Business Cloud PBX with PSTN Calling service provides users with the ability to make and receive traditional phone calls in their Skype for Business client, and to manage these calls using hold, resume, forward and transfer.

PSTN Conferencing is initially available to 15 countries on December 1, with a phased roll out to international markets in the future. Cloud PBX is available worldwide starting December 1. PSTN Calling is available in the U.S. starting December 1, with a phased roll out to international markets in the future.

The fine print: PSTN Conferencing users may incur additional per-minute consumption charges, but customer can disable this feature to avoid additional billing. PSTN Calling is paid add-on for E1, E3 and E5. For E5 users, PSTN Calling costs $24 extra (per user, per month) for international and domestic calling, and $12 for domestic calling only. For E1 and E3, the international and domestic calling plan is $32 extra.