What kind of messaging software is needed to run the following situation/process?

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http://serverfault.com – Not sure if this is the right section, feel free to move it if it needs to be moved. I'm researching what's required to be able to have a process where a large institution like a college can have the faculty send/recieve emails/sms messages from students. Ie, a prof might want to send an update (email/sms) to 500 students in here intro math classes. Or the students might have created study groups, and then want to be able to send msgs to the group members... We're envisioning a frontend, where the user/prof can send out the email/msgs and the "box" would then handle the processesing and s (HowTos)