I am having a lot of trouble when sending to multiple contacts

I have just created a new outlook account. to be used as for EMAIL only. I went in and created my contacts and two different groups containing multiple contacts. If I select only one person and send him an EMAIL it works ok. If I include multiple contacts or use a group that has multiple contacts within it. It does not seem to work. I don't know if it is because I don't know how to use correctly or if there is a problem. Is there somwhere that I can read about correctly using contacts. I have one group with 17 people in it. and one group with 7 people in it. I need to be able to write one EMAIL and send it to a group containing 17 contacts.