#subject_email {
    width: 100px;
    overflow: hidden;
    white-space: nowrap;
    text-overflow: ellipsis;
}

#subject_email:hover{
    overflow: visible; 
    white-space: normal; 
    width: auto;
    position: absolute;
    background-color:#eee;
    border-style: solid;
    border-width: 1px;
    width: 100px;
    display: block;
}

#subject_email:hover+div {
    margin-top:20px;
}