Unable to send azw file to kindle anymore

[Madhursehgal]

Hi, I am new here and am looking for a solution that I couldn't find anywhere.
I don't know if anybody else tried it but the way I send azw files to kindle is by converting a file azw3 in calibre and then saving it to disk and changing the extension to azw. I then send it to kindle through the send to kindle app or by email. It was working absolutely fine a few days ago. I last uploaded a document on September 2nd.
But I was trying to send an azw file to kindle recently and was unable to do it a few days later. Everytime I got an email saying 'there was a problem with the document you sent.' All the other file types like mobi, pdf and txt are all being sent successfully. It just the azw files that aren't.
Also, every time I send the azw file from send to kindle app I get a notification saying your document has been successfully sent. But immediately after this I get the email.
I really liked this way of sending my files to kindle as it automatically read all the right metadata of the file with perfect author name and everything. But when I send it in any other format it's not reading the metadata. I see my name and email address in place of author name.
I spoke to the amazon customer service associates but they were of no help. I don't know why this is happening all of a sudden. I don't think it's from my end though. Maybe it's amazon or maybe it's calibre because I recently updated the software on my pc. Before that it was working fine.
Can anybody please help me with this issue?
Also, I am new here and I don't know how this works exactly. Who will reply to this, if anybody?

[jhowell]

For a brief period Amazon accepted AZW3 files via email. That was apparently a mistake and they are blocked again. Even when it worked there were some problems. Annotations and reading position would not sync for those books.