Microsoft suspended my Outlook.com acccount for spam..a question.

I just started at being officer for a non-profit. I sent out email to our members that number about 300 people with a Forms survey asking about future meeting ideas. When I sent the email, it came back as being unable to deliver to all email addresses in the email (most of which were in the BCC column). I tried sending the email again and ended up with getting my account suspended. I finally was able to get a code to my phone and got my account active again.

My question is would it be safe to send out emails to all our members in the future. From what I read, Microsoft Outlook allows up to 500 people. Our organization  has much less that that. If I used this account again, would I risk it being suspended or permanently disabled again? I only link I had was for a Microsoft Forms survey.