Yes! If you have a campaign or a large batch of emails queued in the backlog, Mandrill reserves an extra 5% of your hourly quota so more critical emails, such as password resets or order confirmations, can send without delay.
Prioritize Important Messages
important option (API) or
X-MC-Important (SMTP) to flag important messages and give them priority over other messages you are sending. The value should be True to prioritize the message and False to not prioritize it.