To view the amount of storage available with your plan, please visit the Pricing FAQ page.
The total amount of mailbox storage is determined by the sum of storage (disk space used) for all mailboxes in the account (domain). That is, the mailbox limit refers to the shared total for all user mailboxes on your domain. For example, if your subscription plan has 10GB of mailbox storage available, 10GB is the total amount of storage for all of the mailbox (email) accounts. If one email account is using 3GB of storage, there will be 7GB of available storage for the remaining mailboxes associated with your account (domain).
A Website Max plan add-on is available for the regular subscription plan. To learn more about this add-on, visit What if I want to increase my mailbox or disk space storage limit?