Windows Live Mail connected to gmail via imap. Won’t send to all members of category.

I have Windows Live Mail 2012 and Windows 7. The WLM is not an upgrade--it's what came with Windows 7. I previously had Outlook Express and XP and could send to groups. Now I create a "category," for instance, of 14 members, and when I enter the group name into the "to" field, the program will send to only one member of the group. At first it sent to 3 members. I've tried everything I can think of and everything suggested online, including reparing Windows Essentials. Is this just a fatal flaw of WLM 2012, or is there a fix or work-around? It's really annoying to not be able to use the group function. I have only two groups, but I send to both of them frequently, and it's a major pain to have to look at my list  and enter each name individually each time. I thought of using a different e-mail client, but I used to use Thunderbird and had problems with that, and getting Outlook would cost about $100. (I have Microsoft Office 2010, but it's a version that didn't include Outlook.) If anyone can help me, I will be MOST grateful.