Microsoft Outlook does not render a lot of CSS that most other email clients do just fine. This unfortunately means that your emails are constraint by really old html standards.
This link gives you a good reference of what you can or cannot do in emails for different email clients.
https://www.campaignmonitor.com/css/
For most companies ourlook is the email client for employees so I would suggest avoid trying anything fancy that most likely will render incorrectly in Outlook.
This link is a good guide.