I have illustrated the differences between what I call an "occupational spam culture" and an "opt-in culture" below.
In an opt-in culture, each and everyone can choose which conversations they want to participate in and contribute to – which most likely will be the ones where they can add most value and which they enjoy participating in. It implies that conversations are open by default and hosted on open platforms. If this is combined with ways of communicating where the sender applies the structure to the communication so that the recipients don’t have to, huge amounts of waste can be eliminated and people can use the time and energy that is freed for value-adding activities and seeking out situations where they can add value with their expertise.
The good news is that there are many proven solutions out there that are just waiting to be adopted. For example, instead of communicating with your project team using email, you can communicate using a team blog. What you will do is to impose structure on the communication by sending the information to a specific context where it gets associated to previously communicated information and becomes available to anyone who has access to the blog. The information will not be buried in people's inboxes, it does not need to be pushed to their inboxes if they don't want it. From an organizational point of view, information and knowledge that can be of use by other people within the organization is captured and made available. Not as a separate activity, but as a biproduct of a communication process.
Even people who are using email by habit can be "lured in" to this kind of communication. Just don't tell them they should start blogging. They can still write their messages in their email clients and send them as emails, but by sending the messages to blogs instead of to lists of email addresses they will put the information in the context where it belongs. Even if the other team members choose to subscribe to the blog via email (as an alternative to visiting the blog or subscribing to an RSS feed), the information will stay on the blog and be available to those who might need it. Once the receivers have read the information, they could delete their emails and still be confident that they can find the information on the blog. In other words, there is no need to spend time organizing those emails in folders in their email client to simplify re-finding the information. They could just visit the blog to browse or search it, or even find it using the enterprise search. Should they choose to comment on the information that was posted on the blog, why not do it on the blog instead where everybody can see who has commented and what, instead of creating numerous messy email threads using reply all?
If it is this simple, and it really is, then what are you waiting for? (ok, there's on part that is hard, and that is making people change their habits)