This has been a big 'feature', but it has not made much of a contribution to the overall body of knowledge that really is required to use a product like word to the best advantage. Unfortunately one of the big selling points of word has always been anyone can bash out a page and a half and make it look ok on paper, and PDF has allowed this to carry over to email attachments. If you want to get functions to transfer, you must be fairly exacting in your implementation. There is only a loose translation between word processing with it's typographical focus being on putting the written word on paper in very specific places and at very specific sizes and HTML which is focused on screen reading. Some twenty years later it is still around and is often the preferred format for documents being send by government and big business, because they can largely control how it looks when viewed online and is very tolerant of poor document layout as it uses the printer language postcript to define the document. One of the first and most successful attempts to do this was the proprietary Adobe document format (PDF). What many folk do not understand is that typograpical functions need to be translated for online viewing. This is the result in Thunderbirds editor. What I can say is using word 2013, I had no issue copying leading indents of half an inch into Thunderbird, but I has created them in word using the correct setting for leading indents, not using tabs which simply do not really exist in HTML. Personally I use freeclipboard viewer to perform such tasks as it not only shows the formats on the clipboard, but provides access to each.

A copy places the information in many formats, everything from words own format to plain text. Then we have to establish if Word actually places that information on the clipboard. Are you talking about hanging indents, initial indents or something else.

Set first line indent in word