Instead of using ifsym, use \usepackage{marvosym}!!

It is greate！！！

\documentclass{IEEEtran}
\usepackage{lipsum}
\usepackage{amsmath}
\usepackage{marvosym}
\begin{document}
\title{This Is an Article}
\author{{Bendan~Ban$^\text{\Letter}$}%
}
\maketitle
\lipsum
\end{document}