Q. Can I change the size of individual mailboxes from 5MB attachments to 10 MB or larger?
A. It really depends on what product you are talking about. If it is GroupWise only, there shouldn't be a limit on regular incoming / outgoing mail attachments unless your administrator has set one. Check with your help desk and ask them if limits have been placed.
If you are talking about user limits on the mailbox, that is also something that is settable via ConsoleOne. But bear in mind, administrators can't set things up for one user, and not the rest. The settings are all or nothing.
If you are talking about attachments that get sent to mobile devices, that's set in either the GroupWise connector or the Mobility connector as well as on the device.