gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
curl -sSL https://get.rvm.io | bash -s stable --ruby
and close and reopen your terminal.
rvm default@mailcatcher --create do gem install mailcatcher -v 0.5.12
rvm wrapper default@mailcatcher --no-prefix mailcatcher catchmail
mailcatcher -f