documentclass[twoside,twocolumn,english,article]{memoir}

pretitle{begin{flushleft}LARGE}
posttitle{parend{flushleft}vskip 0.5em}
preauthor{begin{flushleft}
           large lineskip 0.5em%
           begin{tabular}[t]{l}}
postauthor{end{tabular}parend{flushleft}}

title{My Title}
author{
    First Author\
    first@email.com
and
    Second Author\
    second@email.com
}

begin{document}
maketitle
Hello world.
end{document}

! Argument of reserved@a has an extra }.
<inserted text>
                par
l.54 }

preauthor{begin{flushleft}%
           large lineskip 0.5em%
           begin{tabular}[t]{@{}l}}
postauthor{end{tabular}end{flushleft}}
renewcommand*and{%
  end{tabular}%
  hskip 1em relax
  begin{tabular}[t]{l}}
renewcommand*{andnext}{%
  end{tabular}\ begin{tabular}[t]{@{}l}}

documentclass{memoir}
usepackage{array}
preauthor{largenoindentbegin{tabular}[t]{@{}l@{hspace{1cm}}l}}
postauthor{end{tabular}par}

author{%
    First Author & Second Author\
    first@email.com & second@email.com
}
title{Title}

begin{document}
maketitle
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
end{document}