Email description exceeds 10000 limit but in incident/case entity is get truncated.

Hi CRM Expert,

We having some of the email which the description lenght is exceeds 10000 limit(20,041 characters) .But in the corresponding case/incident description, it is get truncated to just 470 characters. Would like to know why the information in the Description is truncated? And is there any workaround can we increase the description limit in email?

Thanks,