200 mails/day

 Restrictions applied to the daily email limit for a database hosted on our SaaS infrastructure.

But what is an improper use of our email system?**
1) Spam/scam/phishing...Obviously, an email promising any kind of body part enlargement should be considered as malicious. I guess there is no need for a long explanation on why this degrades the rating of our email servers.
2) No "Unsubscribe" link.All newsletters must include an "Unsubscribe" link. The business might be legit, be the customers must have the choice of receiving or not the newsletters. This is defined for each partner in the form view under "Opt-Out": "If opt-out is checked, this contact has refused to receive emails for mass mailing and marketing campaign."Any user clicking on the "Unsubscribe" link will be set as "Opt-Out".
3) The bounce rate- Emails must be sent to existing addresses. Several use cases can appear:- the user imported (semi-)random addresses that he bought online- duplicate email addresses are found in the mailing lists- invalid addresses (deprecated, typo...)When an email server has a high bounce rate, it will be publicly considered as sending emails to random addresses. Ultimately, it is considered as sending spam. An acceptable bounce rate for a mass-mailing is around 1%: this might seem very low, but other mass-mailing providers such as MailChimp or MailInBlue have the same expectations from their customers

Any solution?

sending them one-by-one, not bcc. and the rest: read the manual