JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" placeholder="E-Mail" />

CSS

::-webkit-input-placeholder:after {
   content: '*';
}

:-moz-placeholder:after { /* Firefox 18- */
   content: '*'; 
}

::-moz-placeholder:after {  /* Firefox 19+ */
   content: '*';
}

:-ms-input-placeholder:after {  
   content: '*';
}