Currently the JM must use select all to manually select all users with a given role, which is impractical when there are 1000s of users and multiple pages of user listings.

Some support for this is provided via the Editor's Notify Users, but it's restricted to readers, authors, and subscribers and attachments cannot be included.

We can add a button at the bottom of the JM people listing for each role, i.e. 'Send Email to All', that will produce the standard JM email form, but with the addition of some text below the To: field that indicates that the email will be sent to all users with the selected role.