The space you can have for your mailboxes depends on the kind of hosting plan you choose. The only limit to your mailboxes' size stands in the total disk space of your hosting plan, that you can manage as you wish.
For example, if you choose a KeliCMS hosting plan, you will be provided with 10 GB web space: you can choose to save 8 GB for your e-mails and to dedicate the remaining 2 GB to your website or database, or, in alternative, if you don't have a website, to dedicate the entire amount of space to your e-mails and so on.
So, you will be able to manage your web space and customize it as you need.
