Another option is to rent what is called a "SharePoint" site and configure that for uploads. These are widely available and the cost ranges for nothing, if you have a service that offers this (Comcast, as example offers this with some of their internet services), up to a few $$ per month.
They are pretty easy to configure and can configured as so-called blind uploads – meaning that the sender can send but not see anything on the server, or a site which requires a name/password for access, or a site which has no security, but i don't recommend this.