[odamizu]

In addition to the Send-to-Kindle app and plain old email, one can also email it directly from Calibre if you set up Prefs > Sharing Books by Email. This is usually what I do.

I also prefer dual-mobi so that I get AZW3 on my eink Kindles (and I give up covers as a result, though since I usually use List View rather than Cover View, it's not an issue for me; I know others feel differently).

If one is thinking of going with dual-mobi to get AZW3 on an eink Kindle, be warned that every so often the AZW3 portion of a Calibre dual-mobi seems to fail and one ends up with the old-mobi version instead. I've been trying to figure out what makes it fail, and it seems to be a Calibre problem, because if I convert the exact same epub using KindleGen, it works fine. If anyone has any insights into this (problem with opf? css? html?), they would be welcome.

Also, if WhisperSync is important to you, sometimes that will fail, too. I've found that simply re-sending the same file sometimes solves the problem. Other times I'll give the book a new title (e.g., Title2). Worse case scenario: KindleGen so far has always solved the problem. Again, any insights into what's causing Calibre-converted mobis to fail would be most welcome.