Hi, I'm Bhavik. Welcome to JustAnswer. I'm reviewing your question now, and will reply back ASAP.
The maximum number of recipients in an email is 100 - that includes To, CC, and BCC all together. And Yes there is no way currently to increase this limit as t we get a bounce message from the mail servers when we try to send to >100 recipients (using Outlook 2010). This is sent by the servers, not by the mail program itself, so you should get it no matter what mail program you use.
Telstra do offer a mass mail pack which you can purchase and should allow you to use the Telstra (ie not BigPond) mail servers to send bulk messages.
Below link is for your reference :-
I hope , I answered your question . Let me know if you have any other question for me