There is no such limit to allocate the email space for the single email account in Linux shared hosting. However, you need to utilize it from the total available space you have in your Linux shared hosting plan.
Available Total Space Per Plan in Linux Shared Hosting Service.
|Personal Web Hosting Plan||Small Business Web Hosting Plan||Enterprise Web Hosting Plan|
|10 GB||30 GB||50 GB|
Looking to get more details on Shared Linux Hosting Resources? Please refer to Linux shared hosting resource details.