sign up for multiple email acounts

I am again having trouble signing up multiple email accounts in a day for my classes at a senior citizens center.  We teach our students how to sign up and use an outlook email account.  Since I have 24 students a day the daily limit is too small. In the past a microsoft representative added the IP range that I had provided to their white list permanently and it worked great.  We have changed our Internet service so that is probably why we are having problems.  I have tried to email using the addresses from the last time I had this problem and tried calling for support.  I was told to use this site.  Hope this work.