I've tried to use K9 mail and Thunderbird for Android, and with both have had issues sending an email or replying to one and having my email dropped without any notice. I've found that this happens all the time when I send to my own Gmail account. I can send from Tbird for Android to another of my own domains on Hostgator. I can send from my desktop version of Thunderbird to my android version, and to Gmail. Even if I import the desktop configuration to Android, I can't send from it to Gmail, and no notice of failure comes back. Any ideas?