There may be times you need to paste content from an external source, such as Microsoft Word, into one of your messages. When doing so, keep in mind that what you see in one program may be different than how it will display in your message. Why? Because of the likely inline formatting you'll be bringing along with it.
EXAMPLE: In Outlook emails, you might notice text appearing crossed out or with strikethrough-like artifacts due to hidden formatting brought over from external sources.
Typically, it is recommended that you do not copy formatted text from another platform and paste it into an email message in the Message Editor because other platforms introduce inline styles and other things that may not be compatible with email messages. This unseen formatting can also negatively impact your deliverability.
If you must copy content from an external source, paste it into the Message Editor using the Paste from Word option or the Paste as plain text option next to it.
This will strip out most of the extraneous code. But even these tools are not impervious; there are still some issues that you can run into, like invisible characters and hidden HTML elements that aren't visible until the message lands in your inbox or Deliverability Testing.
TIP: Alternatively, you can paste the text into a plain-text editor like Notepad to strip hidden formatting or use an HTML-cleaning tool before copying it into the Message Editor.