Box integration is sending unusal format to emails resulting in + between each word. This was reported and found Thanks for testing and sharing your observations. The behavior you’re seeing with the + signs in the subject and body is due to how the Box integration generates the Outlook on the web compose window. It URL-encodes spaces as +, which Outlook sometimes displays as spaces and sometimes shows literally — this explains why clearing the browser cache makes it look correct for the first attachment but not for subsequent ones.

Essentially, this is a limitation of how the integration constructs the subject and body text, not an issue with your browser or Outlook on the web itself. Cache-clearing temporarily loads a fresh script that behaves slightly differently, but it doesn’t fully change the underlying encoding behavior.

At present, there isn’t a reliable client-side fix. The only way to consistently get properly formatted subjects and links would be for the integration to generate the email body and subject using HTML or encoding via Microsoft’s Graph API rather than plain URL-encoded text