whenever i travel i like to use kindle for reading some articles that i’ve earlier collected. for collecting i use a simple PHP script with rich text editor that allows me to copy & paste content and then mail it to my kindle address.
recently i’ve started getting requests from Amazon to approve each document sent to kindle:
We received a request to send the following document to your Kindle account: * 202104051845testtt_.html.pdf Click below within 48 hours to verify this request. Why did I receive this email? Kindle takes your account security seriously. To help ensure you only receive documents from sources you trust, Kindle has added an extra layer of protection to your account. Learn more. Prefer to skip the verification step next time? Edit your Send to Kindle email address (....@kindle.com) by visiting your Preferences in Manage Your Content and Devices. After editing, be sure to notify your approved senders to ensure uninterrupted delivery of your documents and newsletters. Amazon Logo
i’ve found suggestions to change my @kindle.com mail to more unique, that did not help. my sender’s address was already on the “Approved Personal Document E-mail List”.
what was the solution? stop spoofing email@example.com from my PHP code and start using another domain name for the FROM field in messages sent to @kindle.com address. Amazon must have caught up and started checking DKIM/SPF of the incoming messages.