It should have 250 mb storage, but no there isnt' a way to increase it.
The primary gets 2gb
I would simply try a different free service if you needed more space.
Seriously? Your suggestion is to go to a free email provider?
I am paying for email and internet, and sub-accounts only get 250 MB? What is this 1998 with Prodigy?
Completely unacceptable that verizon only gives 250 MB to sub accounts. My cell phone from 8 years ago had more storage space.