In one sentence, describe what the following article is about:

Lack of format support is the most common issue for loss of formatting when copy/pasting between web and non-web software.  Most modern email clients or office software will enable HTML formatting by default, whether it’s a web client, like Gmail/Google Docs, or a separate piece of software, like Microsoft Word/Outlook. Software that is either very old or very simple, like WordPad, Notepad, or TextEdit will not support HTML format. It is possible that HTML formatting is supported but has been disabled. You can usually toggle this manually in the options. Enabling this option will vary depending on the client being used. Typically you will want to look for an option labeled “HTML Format” or “Rich Text” in the options section of the client or in the text composition window. For example, formatting options can be toggled in Outlook in Tools > Options > Mail Format. Once both programs you are copying from and pasting to are using HTML formatting, you can copy/paste formatted text as smoothly as any other text.

Summary:
Check that HTML formatting is supported by your software. Enable HTML formatting. Copy/Paste complex formatting.