Why won't deleted emails from cell phone auto delete on iPad?

[dlhoff0608]

When I delete my emails from my Sprint HTC EVO phone they automatically delete from the Comcast server. Why won't they auto delete from iPad?

Every time I look at email on iPad I've to manually delete hundreds in order to remove. Can't it sync via wi-fi just like my cell?

If I read email from a computer via Comcast website, whenever I delete from their server it auto syncs deleted emails to cell so I don't understand why it can't do the same for iPad2?

Is there a feature I need to turn on?

Thanks!