Is there any way you can set a per mail box limit with the network solutions one?

If the email needs to be read in various places, it's not going to work downloading it to individual computers to say outlook and deleting it from the server.

It is quite possible to set up your own IMAP server and have as much disk space as you want. I do that at home using fetchmail, postfix and cyrus on linux. All our email from our various email accounts is placed on this server. My setup is really only for convenience at home though. I can access it on my phone via VPN if I really need to from outside but the IMAP server is not accessible outside the LAN. I'm unsure as to what security steps would be needed to do this.