Guide · Updated 24 October 2026 · About 6 minutes
Send to Kindle error E999 (or an EPUB that won't go through): eight fixes
You sent an EPUB to your Kindle and got an email back saying E999, or it simply never arrived. Amazon's error code table describes E999 as a "Send to Kindle internal error" and suggests trying again later. Sometimes that's all it is. But if other files go through and this one fails every time, the problem is almost always inside the EPUB. The fixes below are in order: quick checks first, then repairs.
Disclosure: we make ArticleFerry, a browser extension mentioned in fix 8. Every other fix works without it, mostly with the free Calibre app.
1. Rule out a temporary fault
Send a small file that you know works, such as a short TXT or a different EPUB, to the same address. If that fails too, it's Amazon's side: wait a few hours and try again. If the test file arrives and your EPUB still fails, carry on below.
2. Try Send to Kindle for Web
Upload the same file at amazon.com/sendtokindle. It takes files up to 200 MB, while email is limited to 50 MB per attachment (Amazon help). If the upload works, the file is fine and your email setup is the problem; our guide to Send to Kindle email problems covers that. If the upload fails too, the file needs fixing.
3. Give the book a language
Calibre users widely report that an EPUB with a missing or invalid language tag (blank, und or a made-up code) is a common cause of E999. In Calibre, select the book → Edit metadata → set Languages to the book's real language, such as English → OK. Then convert it EPUB to EPUB (fix 5) or use Save to disk, so the new tag is written into the file.
4. Check it isn't DRM-protected
EPUBs bought from stores that use Adobe DRM, such as many Kobo and Google Play Books titles, can't be sent to a Kindle. Amazon refuses encrypted files (E004). Read those in the store's own app or on a compatible e-reader. Removing DRM breaks most stores' terms, so we don't cover it here.
5. Rebuild the file in Calibre (EPUB to EPUB)
In Calibre, select the book → Convert books → output format EPUB → OK, then send the new file. Converting to the same format rewrites the HTML, the table of contents and the package file, which clears many small errors that make Amazon's converter give up. It's the single most effective fix.
6. Repair or remove what Amazon can't convert
Open the book in Calibre's editor (right-click → Edit book) and run Tools → Check book, then let it fix what it can. Amazon's own list of elements its converter struggles with includes SVG images, audio and video, mathematical equations, images with linear gradients, footnotes inside footnotes and very large tables (see E013 and E016 in the error table). Embedded fonts are another frequent suspect in user reports. Calibre's free Modify ePub plugin can remove them in one step, and the Kindle's built-in fonts are fine for most books.
7. Validate it with EPUBCheck
EPUBCheck is the official W3C validator for EPUB files. It's free and runs on any computer with Java. Errors it reports, such as a broken manifest entry, a missing file or a badly formed chapter, point to exactly what to fix. A file with zero EPUBCheck errors is far less likely to fail at Amazon.
8. If it's a web article, make a fresh EPUB
EPUBs saved from web pages by older tools often carry odd markup from the original site. ArticleFerry makes a clean EPUB 3 from the article you're reading, with a language tag, a cover and plain chapters. We test its files with EPUBCheck and get zero errors. See how to send a web article to your Kindle and how to convert a web page to EPUB for the other options too.
Try ArticleFerry. Free: turn a web article into a clean EPUB on your device and send it to your Kindle.
FAQ
What does E999 mean on Send to Kindle?
Officially it's an "internal error", and Amazon suggests trying again later. In practice, when the same EPUB fails again and again while other files work, it usually means Amazon's converter couldn't process something in that file.
Why does my Kindle say an EPUB isn't supported?
Kindle e-readers don't open EPUB files copied over USB. EPUBs have to go through Send to Kindle (email, the web uploader or the app), which converts them for the Kindle.
Can I send a fixed-layout EPUB?
Often not well. Amazon may deliver it with its original layout and no adjustable text size (E016), or fail. Picture books and comics usually read better as PDF.
Will converting in Calibre change my book?
It keeps the text, images and chapters, but it may simplify styling. Keep the original file until you're happy with the result.