Timer Gmail Free
This app can send G-Mail by specifying the date and time.
The paid version add the function to notify schedule status.
And, the function to send mail immediately.
There are other apps -> https://market.android.com/developer?pub=in-trinity
YouTube -> http://www.youtube.com/user/intriandroid
Twitter -> http://twitter.com/#!/In_Trinity
Facebook -> http://on.fb.me/vDUVnp
Download