Fix the E999 Send to Kindle error漫

It is Amazon's catch-all code for a failure inside their own document converter. The upload itself worked, so the problem is not your email address, your approved sender list or your Wi-Fi. Something in the file stopped their converter part way through, and the code deliberately does not say what.

In practice: page images far larger than any Kindle screen, so the conversion runs out of room; an EPUB whose ZIP structure or OPF manifest is malformed, often from a tool that wrote it badly; embedded fonts or CSS the converter cannot resolve; and sheer size, since a volume near the transfer cap leaves no headroom. Rebuilding the book from its pages removes all four at once, which is why it works without knowing which one applied.

Because E999 is a property of the file, not of the attempt. Nothing about the second email is different, so Amazon's converter reaches the same point and stops. Resending only helps when the first failure was a genuine timeout, which is rare.

No. Title, series, volume number, author and cover are written into the rebuilt EPUB, so the book lands in the Kindle library sorted correctly and with its own art rather than its first page.

Yes. Copy the EPUB over USB into the documents folder, which has no size limit and no converter in the path, or fetch it on the device from the Reader Shelf over Wi-Fi. Both skip the step that produced the error.