Forefront Protection 2010 for Exchange was an antispam/antimalware product that was used heavily with Exchange 2010, especially in greenfield projects.
Microsoft stopped developing the product in 2012, but continued to provide virus updates and signatures. This is coming to an end on 31st Dec 2015. As an Exchange admin, this is the time to start evaluating alternate products and mapping out a plan to replace FPE 2010 with your chosen product.
If your subscription for FPE 2010 expires before Dec 31 2015, you will not be able to renew it. You will continue to get updates till the end of the year though. In short, you have another 10 months to plan for the transition.
If you have moved to Exchange 2013, you can make use of the basic antimalware protection that is baked into the product. You can increase the defense by going for a cloud solution on top of it like Exchange Online Protection (EOP).
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