Help Please. Unable to send message;Reason:550 5.4.6 Mail rate exceeded limit

Help Please. Unable to send message;Reason:550 5.4.6 Mail rate exceeded limit

Dear Zoho Team,

Please help us with the condition of Unable to send message;Reason:550 5.4.6 Mail rate exceeded limit.

Actually we use our user for mass mailing or send email to multiple user with BCC because of announcement to our partners.

After the first we got the warning Unable to send message;Reason:550 5.4.6 Mail rate exceeded limit , we wait about 30 minutes to get use the user again.

After some time we use mass mailing again we got the same warning/notice.

Is ther any solution so we can avoid that condition ?

Because we only send three times mass mailing and got blocked by the system.

Thank you so much and we hope get some breakthrough for this problem.