app/views/meetup_mailer/notify_publication.html.erb
<!DOCTYPE html>
<html>
<head>
<meta content='text/html; charset=UTF-8' http-equiv='Content-Type' />
</head>
<body style="text-align: center">
<img src="<%= root_url %>/logo_base.png" style="width: 80%; margin: 0 auto;"/>
<h1><%= I18n.t 'meetup_mailer.greeting', user: @user.username %></h1>
<p><%= I18n.t 'meetup_mailer.notify_publication.body', user: @user.username, meetup: @meetup.title, date: @date %></p>
</body>
</html>