There isn't a TeamDynamix control for the rate at which messages are sent out of the system, unfortunately.
While we do not have explicit documentation on achieving it, we have recommended other clients might consider using an O365 connector, which has different limits than using a standard user account. You can find information about those here: https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/use-connectors-to-configure-mail-flow
That would be an option for getting around some of the O365 limits.
Give that a read and let me know if any additional questions arise and we'll do our best to assist.