Just finished my first (real) Android App and wanted to deploy it in my phone (not just in the emulator).
So I sent an email to myself with the .apk attached as several tutorials said that you can just open it from your mail to install the app.
On the phone, I opened my mail app K9 and opened the .apk. But instead of installing I unfortunately just got
Beim Parsen des Pakets ist ein Problem aufgetreten. (in english) Parse Error: There is a problem parsing the package.
even though the minSdkVersion was set correctly.
The solution was rather simple: Do NOT open the .apk in K9 directly but save it to the sdcard and open it via a filemanager like Astro.