Outlook does not support certain CSS properties such margins used to center images. Here is a full list of CSS support by email client. Any margins created within the rich text modules in email will work in most major clients except for Outlook.
To center an image in Outlook, you will need to access the Source Code of each applicable rich text module in your email.
- Navigate to Content > Email and select an email to edit.
- In the rich text module with your image click the Source Code button (<>) or go to Tools > Source Code <>
- Locate the code for the image you are trying to center that begins with '<img'
- Add <center> </center> or <p style="text-align: center;"> </p> tags around the img code. For example:
<p style="text-align: center;"><img src="http://www.hubspot.com/test.jpg"></p>