With Mercury there are no limits to how many messages you can send. Once you have purchased the FULL plan, which includes sending bulk messages, you can send as many messages as you want.
This means that you won't have to worry about respecting a maximum sending limit.
But you have to keep in mind that there is a limit that consists of the average speed of sending per day.
To maintain the sending speed it is important to respect the conditions that we have explained in the best practices for sending.
About the average sending speed, we can send about:
1500 text messages per hour (about 25 per minute)
36000 text messages per day