Not surprised at all. The Samsung email app seems to be broken. Lotsa people are having various problems with it. There are posts about email trouble on Samsungs everywhere.
The best fix is to try another email app. There's plenty of good ones to choose from such as My Mail, Maildroid, K-9, Cloud Magic or my favorite, AquaMail, just to name a few.
Android since v1.0. Linux since 2001.