I use multiple methods for wirelessly sending things to Kindle:
- Send To Kindle in browser (Google Chrome add-on)
- Send To Kindle from folder (system download)
- Send To Kindle from email (using my Kindle address)
- Send To Kindle from Calibre (using my approved email address to pass through)
Sometimes the document will bounce back to me, saying it couldn't be processed. When that happens, I'll try one of the other send methods. If it fails a second time, I try to figure out what the issue was and if all else fails I'll reconvert it in Calibre. Since my main Send To Kindle actions are because I want to send an article or a fanfiction story to my Kindle, the need to reconvert usually isn't reached.