I know the idea that we can ever replace emails is a scary one, and the truth is we can't really replace them. Emails are great for interacting with external organisations as we have no better alternative, but for internal interactions we have an alternative - SharePoint. Email is a problem for any organisation, we are overburdened by the amount of emails we receive, each one pops up at the right hand side of our screen screaming at us to attend to them, we silo information in our emails that cannot be shared with the organisation, in short they are not working for internal communications. SharePoint has many great features that can help us move away from relying on email and gain some control on how we manage our interactions and the information generated from them.
Announcements lists are designed for storing communications that need to go out to a group of people but do not require a response. For example, reminders of maintenance, reminders of upcoming events, etc. As emails this information often go out to the entire organisation (weather they wanted them or not) but there is no response required from the individuals. Using the announcements list this information can be stored and users can consume the information as they like (see the last point on alerts for more information on this ). Another great feature is that past announcements can be stored, giving you an auditable communication trail between you and a group of people.
There is nothing worse than opening up your email in the morning to see that you have been included in a large email chain, you know the type sent out to 10 people directly and another 10 CC'd in for good measures. These email chains are difficult to manage as not everyone will reply all, it's difficult to share and it clogs up your inbox. Discussion boards are a great way to replace the majority of bulk emails, they allow one person to post a discussion and multiple people can respond. There use lies in the fact that they become a centralised searchable knowledge base. The comments and insights you have gained from the team are then stored and can be used again by other teams. Given the amount of crucial decisions made in emails capturing them in this way makes it easier to audit and provides a backup to prove any decision making.
By implementing these two features you can look to decrease email traffic, but the success of these features is dependent on users accessing the sites that have the announcement list or discussion board. If users have lots of sites to look at it cannot be guaranteed that they will always see when new content has been added. To make it easier they can set an alert up on the announcement list or discussion board, when any activity takes place they are then emailed to tell them to check the site. Yes, I know what you are thinking this creates another email and I thought we were trying to get away from them, but this email can be deleted once it has been read as the actual content is in SharePoint.