With so many Outlook apps and services, it can be confusing to know which version you're using. To find out, choose how you access Outlook:
Outlook is an application for managing your email, contacts, and calendar; also known as email client. Follow these steps to find out which version of Outlook is installed on your computer.
In Outlook, choose File.
Select Office Account.
If you don't see Office Account, option, choose Help. You'll see the product version on the right side of the page.
You'll find your version and build number under Product Information. For example, the following displays for Microsoft Office 365 ProPlus, which includes Outlook.
If you need to know whether you're using the 32-bit version or the 64-bit version of Outlook, select About Outlook.
The top of the About Outlook box shows the version number and 32-bit or 64-bit distinction.
For more info on email client, visit this link.