You can add as many MX records as you want, although keep in mind that they must be from the same provider. As MX records from different providers won't work.
In case you wish to use Hostinger email services, you can check MX records here: Where can I find MX records?
It's highly recommended to keep an eye out for the priority values you set - lower values denote higher priority (0 being the highest possible priority). If you assign multiple mail servers the same priority, your mail will be distributed to the servers of the same value randomly, which can cause issues