for email admins
Topics in this area:
email client settings
email clients' configuration examples: Outlook - Outlook 2007 - Outlook 2013 2016 - Mac OS/X Mail - Thunderbird - Zimbra Desktop
email server settings
email servers' configuration examples: Microsoft Exchange Server - Microsoft Office 365 - Zimbra Collaboration
doublebackup app
transparently archives all the emails
spamstop app
spam filter based on email authentication and authorized senders