Thank you for reaching out to the Community! What version of the Outlook app are you using? What mobile device are you viewing your email through? Based on the details you have described, it sounds like your email is not being mobile responsive. Are you using an iPhone? If so, what version of iOS?
We have seen cases where emails are not mobile responsive in the Outlook mobile app for iPhones. This experience happens due to recent updates Microsoft has made. These updates cause the code that we use for mobile responsiveness no longer works in the Outlook Mobile App for an iPhone. Because of this we suggest viewing the email campaign in a different mobile email client. This is an experience we are continuing to troubleshoot. What is the name of your campaign and your web hosting provider? This is helpful information to track in your account.