Email is a large topic, below you will find the most common items.  

Managing the Inbox:

Microsoft Outlook users can experience poor performance when the heavily used core folders (Inbox, Calendar, Sent Items, etc.) contains large number of items.

To Maximize Performance: 

• Maintain less than 20,000 items in the Inbox.
• Maintain less than 20,000 items in the Sent Items
• Maintain less than 10,000 items in the Calendar
• Maintain less than 10,000 items in the Contacts

General Email:

• How to Recover Deleted Items in Exchange
• How to Set Delegate Access in Exchange for Mailboxes and Calendars in Outlook for Mac
• How to Set Delegate Access in Exchange for Mailboxes and Calendars in Outlook

Public Folders:

• How to locate and open a Public Folder
• How to Add a Public Folder as a Favorite in Outlook for Windows
• How to Access Public Folders in Outlook for Mac 2016

Send As:

• How to Send As from another email address in Outlook for Windows
• How to Send As from another email address in Outlook for Web App (OWA)