It is sometimes amazing to note that we miss such obvious things in Salesforce. For example, before today if you asked me send a mass email to all Salesforce users informing them about something (e.g. an upcoming maintenance window or a new Salesforce feature), my first thought would have been to create a report of all actives users in Salesforce with their email addresses, download the report and then send an email using my email client.
I did not not realize that Salesforce has “Mass Email Users” feature, that allows you to do just the same, right from within Salesforce. And the option appears just below the “Manage Users -> Users” option, where I must have gone hundreds of times.
Navigate to Setup -> Manage Users -> Mass Email Users. Select an existing list view or create a new list view, select an email template, specify the delivery option and send. It is as simple as that.