When using the Email Designer in ACS, editing the preheader is a rather unintuitive task. Clicking 'just the right spot' between whatever structures you have in an email and the menu to the right to make the preheader field appear can be pretty tedious - especially since many of my colleagues use MS...

I've encountered the exact same issue. The problem was a linebreak in the subject line after the actual text contents of the subject line - hence, it was not visible. It makes no sense to enable the ability to create line breaks if it ends up causing errors. The issue has occurred several times sinc...