"Attached file" refers to the file included in the email. "Comments" could mean many things, like "opinions" or "notes." "For my comments" is actually associated with the overall sentence structure, not "the attached file." Think of it like this: "Please refer to ______ for my comments." This would mean that the person is asking you to access the ______ for the purpose of viewing or reading their comments. This blank (______) can be replaced with any noun that makes sense in the situation. For example, "Please refer to the document for my comments." So, in your example, you must open/read/view the file in the email to see the comments.

They should have attached a pdf or word or other type of file to the email which I presume has comments on the plan. Once you open this document you should see the comments. Perhaps they forgot to attach the document before they sent it? (I do this all the time!). Does that help?

"The attached file" is a file that's been included with an email. That's where you need to look to find the writer's comments.