[mjfriedman]

I'm having this problem consistently across multiple recipes: Calibre emails file to Kindle address, producing this rejection email from Amazon (first part below). Really appreciate advice/assistance!

Dear Customer,

The following document, sent at 06:43 PM on Fri, Jan 01, 2021 GMT could not be delivered to the Kindle you specified:
* The Economist.mobi


The Kindle Personal Document Service can convert and deliver the following types of documents:
Microsoft Word (.doc, .docx)
Rich Text Format (.rtf)
HTML (.htm, .html)
Text (.txt) documents
Archived documents (zip , x-zip) and compressed archived documents
Mobi book

Images that are of type JPEGs (.jpg), GIFs (.gif), Bitmaps (.bmp), and PNG images (.png).
Adobe PDF (.pdf) documents are delivered without conversion to Kindle DX, Second Generation and Latest Generation Kindles.

Adobe PDF (.pdf) can be converted to Kindle format and delivered on an experimental basis.

If the document that failed belonged to one of the above document types, please ensure the document is not password protected or encrypted. Note that the Latest Generation Kindles support password protected PDFs.

Helpful tips for personal document attachments:

The file size of each attached personal document should be less than 50MB (before compression in a ZIP file)

The email submitted should not contain more than 25 attached personal documents