The End of Mobi

I received this interesting email from Amazon the other day after I'd sent an ebook, in mobi format, to my Kindle via email. Here was the content:

Dear Kindle Customer,

Thank you for using the Send to Kindle service to send personal documents to your Kindle library. We noticed that the following document(s), sent by you at 07:50 AM on Monday, October 10, 2022 GMT are in MOBI (.mobi, .azw) formats: froudes-history.mobi.

We wanted to let you know that starting August 2022, you’ll no longer be able to send MOBI (.mobi, .azw) files to your Kindle library. Any MOBI files already in your library will not be affected by this change. MOBI is an older file format and won’t support the newest Kindle features for documents. Any existing MOBI files you want to read with our most up-to-date features for documents will need to be re-sent in a compatible format.

Compatible formats now include EPUB (.epub), which you can send to your library using your Send to Kindle email address. We’ll also be adding EPUB support to the free Kindle app for iOS and Android devices and the Send to Kindle desktop app for PC and Mac.      

 If you have any questions, please visit our help page or contact our Customer Service team.      

 Regards,

Amazon Kindle Support

This is the 6th generation Paperwhite Kindle that I'm using

Well it's long past August 2022 but I seemed to succeed nonetheless. Mind you the mobi version I sent proved virtually unreadable with all sorts of bizarre artefacts and so I had to resend it in PDF format.  This Wikipedia article explains what's going on:

Kindle File Format is a proprietary e-book file format created by Amazon.com that can be downloaded and read on devices like smartphones, tablets, computers, or e-readers that have Amazon's Kindle app. E-book files in the Kindle File Format originally had the filename extension .azw; version 8 (KF8) introduced HTML5 & CSS3 features and have the .azw3 extension, and version 10 introduced a new typesetting and layout engine featuring hyphens, kerning, & ligatures and have the .kfx extension.

History

Kindle devices and apps are designed to use Amazon's e-book formats: AZW that is based on Mobipocket; in fourth generation and later Kindles, AZW3, also called KF8; and in seventh generation and later Kindles, KFX. Kindles now support the EPUB file format used by many other e-book readers. Similar to EPUB, Amazon's file formats are intended for reflowable, richly formatted e-book content and support DRM restrictions, but unlike EPUB, they are proprietary formats. AZW files debuted with the first Amazon Kindle in 2007.

Software such as the free and open source Calibre, Amazon's KindleGen, and the email based Send-to-Kindle service are available to convert e-books into supported Kindle file formats. Kindle devices can also display some generic document formats such as plain text (TXT) and Portable Document Format (PDF) files; however, reflowing is not supported for these file types.

In late 2011, the Kindle Fire introduced "Kindle Format 8" (KF8), also known as AZW3 file format. AZW3 supports a subset of HTML5 and CSS3 features,while acting as a container for a backwards-compatible MOBI content document.

In August 2015, all the Kindle e-readers released within the previous two years were updated with a new typesetting and layout engine that adds hyphens, kerning and ligatures to the text; e-books that support this engine require the use of the "Kindle Format 10" (KFX) file format.[8] E-books that support the enhanced typesetting format are indicated in the e-book's description on its product page.

In 2017, Amazon released Kindle Create, a tool that can convert Microsoft Word files to Kindle file format.

In 2022, while the Send-to-Kindle service only supported the original .mobi/.azw ebook formats (along with some other non-ebook file formats),[10] Amazon announced removing this support in favor of .epub which will be converted to Amazon's KF8 (.azw3) from late-2022.

In light of this news, I've just sent a epub file to my Kindle via Amazon's email service. I grabbed the book off the Internet Archive. It's titled "English Biography" by Waldo Hilary Dunn, 1882-1969, and was published in 1916. It might be interesting but the point is to check that Amazon will convert the epub format into a Kindle readable format. The result was disappointing:

Dear Kindle Customer,

The following document, sent by you at 11:56 AM on Tuesday, October 11, 2022 GMT, could not be delivered to the address you specified: englishbiography.epub

Send to Kindle supports the following document formats:

Adobe PDF (.pdf)

Microsoft Word (.doc, .docx)

Rich Text Format (.rtf)

HTML (.htm, .html)

Text (.txt) documents

Archived documents (zip , x-zip) and compressed archived documents

MOBI (.azw, .mobi) (will not support the most up-to-date Kindle features for documents)

JPEG (.jpg), GIF (.gif), Bitmap (.bmp), and PNG (.png) images .

Additionally, Send to Kindle emails now supports EPUB (.epub). Later this year, we’ll also be adding EPUB support to the free Kindle app for iOS and Android devices and the Send to Kindle desktop app for PC and Mac.

If the format of the document that failed is supported (listed above), please ensure the document is not password protected or encrypted, and try sending it again.

You can learn more about sending personal documents to your Kindle in our product info pages: https://www.amazon.com/sendtokindle

If you would like immediate assistance, please contact customer support at +1-866-321-8851 (US customers) or +1-206-266-0927 (International customers).

Yours sincerely,

Amazon Kindle Support

The letter doesn't make much sense. The mobi format is still supported whereas, in practice, the epub format is not. Hmmm. Things seem to be in a state of transition at the moment and maybe there will some sort of resolution later in the year.