When I open any Office 2013 application, there is a yellow banner under the ribbon that literally shouts "GET THE NEW OFFICE It's one of the perks of having Office 365." There is an X at the right-hand end of the banner that allows you to dismiss the banner. Unfortunately, the banner reappears every time I switch to a different email account in Outlook. I have not found a way to turn off this unwelcomed, intrusive invasion by Microsoft.
You can disable this banner by setting a registry key. After you set the key, you'll need to reboot Windows for it to take effect.
If the banner doesn't disappear, set these keys as well:
Do It For Me
Use Group Policy
Businesses using Group Policy can block the automatic updates using the updated Office 2013 group policy template. Look for the option to block updates under Computer Configuration\Administrative Templates\Microsoft Office 2013 (Machine)\Updates.
Double click on Enable Automatic Upgrade and choose Disabled, then click Apply and close the dialog. If Outlook is open, close and restart it.
The Copy command is missing from the right-click menu in Outlook's Calendar; use the keyboard shortcuts or Ctrl+drag to copy appointments instead.
Live Mail will no longer sync calendar and contacts with Outlook.com after the account is migrated to the new server. You will be able to use it for email, using IMAP (preferred) or POP3.
How to change the number of recent files shown in Outlook 2016's Attach File recent files list.
How to block email from specific domains in Outlook.com using a rule.
Error code: 0x86000c1f when attempting to Outlook.com accounts to Windows 10 Mail app or Windows Phone.
Although I don't recommend pulling Office 365 business mail into a personal Gmail account, I know some users do this. For many, it just works, but others receive errors when they try to set Gmail up to use the Office 365 or Outlook.com SMTP server.