What is the maximum email I can have?

You are limited by 2 factors.

1. The quota you have assigned to a particular mailbox, by default the system assigns 10 megabytes but you can change that larger or smaller. See the Cpanel documentation on this feature.

2. The amount of storage available on your account. If for example you have a 50 megabyte account and your web pages take up 25 megabytes, you would have a total of 25 megabytes available to all of your email accounts regardless of what individual mailboxes are set at.