Hi NCVA,
1. Yes. There is a 500 recipients limitation per message, a 10,000 recipients limitation per day.
2. Yes. Of course you can. It is available to send an email less than 500 recipients in one message.
3. Yes. The maximum number of e-mail messages that can be sent from a single e-mail client is 30 messages per minute.
4. Yes. For sending emails, there are no difference between OWA and Outlook client.
5. No.
6. The only way to achieve this goal, please refer to the 2nd question.
7. Yes. If you don’t use distribution groups(lists), The Enterprises users can do everything like the Small Businesses users.
8. 500. For the detailed information, please refer to the article: Message and Recipient Limits.
Thanks,
Maggie Li