In a recent communication, Amazon has alerted Kindle users about significant changes set to take effect from next month. The notification pertains to the phasing out of support for sending MOBI (.mobi, .azw, .prc) files through the “Send to Kindle” feature, starting November 1, 2023. This change, as News18 pointed out, specifically impacts users attempting to send MOBI files via email and Kindle apps on iOS, Android, Windows, and Mac.
it’s trivial to mass convert mobi to a widely supported format. I think this is a welcomed change, because Amazon was the only one on the industry still promoting a legacy format like mobi, even if they tried to start moving on with their newer formats.