Mass emails

Good afternoon,

I help manage an organization for Special Needs Children and Adults.  We sponsor adapted Sports activities as a way to build relationships, teach teamwork, and self-esteem.

I set up a separate email for the group from which I am attempting to send group emails.  These emails go to anywhere from 50 to 250 users.  I manage the list outside of Outlook: I create character strings of email addresses using excel and paste them into the BCC: line in Outlook.  I am using the new Outlook.

Recently, that user (an outlook.com user) is blocked frequently and I have to go in and revalidate it.  The message I get says I am violating the usage rules, but it does not tell me how.

I was going to look at a CRM system, but that adds a ton of baggage: all is want to do is send emails.  

Does anyone have any ideas for how to accomplish what I am trying to do?  I have names and addresses in an excel file and if I knew how I could do a mass import into Outlook.  I would do that if it would fix the problem.

I would appreciate any input.

Jim