Append text to the title

Question

In a class file I want to append an email address to the title. My naive approach was:

\AtBeginDocument{
  \title{\@title – [email]}
  \maketitle
}

But this just doesn't work. If I do \@latex@error{\@title} afterwars for debugging purposes, I still get the old title. What am I doing wrong here and how would be a correct approach? (Also, \def\@title{…} didn't work and \def\oldtitle\@title \title{\oldtitle …} did neither)