Why is the email preview in a CM campaign ("template") not displaying correctly?

On a CM Campaign in Salesforce, the email sent to recipients can be viewed as a template. It won't have merged subscriber data filled in, like a greeting or opportunity close date. In some orgs, this template may not display correctly on all browsers. This is a known issue with how Campaign Monitor frames in their email content. While we can't address that directly, we have added a workaround. 

In CM Settings, on the General Settings page, enable the setting Open Campaign Monitor window in new tab.

This will ensure all links to Campaign Monitor within Salesforce will open in a new tab, without the need for framing.