I happen to receive emails containing tables, and the first table and anything trailing it doesn’t survive the translation to Markdown. This makes messages break off abruptly, which is very confusing for users. They can read the original HTML email by clicking the little envelope, but that’s hardly user-friendly and should probably be regarded as a bug.
Editing the message and pasting the raw HTML table into it seems to work well. Why not do this during Markdown conversion?