A working example of pony and sinatra.

pony-example.rb

# You need to install these gems. 
# - smtp_tls
# - pony

post "/contact-us" do
  Pony.mail :to => 'pedro.delgallego@gmail.com',  
    :from => "#{params[:email]}",
    :subject => "Contact SFT :  #{params[:name]}",
    :body=> "#{params[:body]}, --- Contact Address #{params[:email]}",
    :via => :smtp,
    :smtp => {  
      :host   => 'smtp.gmail.com',  
      :port   => '587',  
      :tls    => true,  
      :user   => 'pedro.delgallego',  
      :password   => 'your-gmail-password',  
      :auth   => :plain,   
      :domain => "your-domain."
  }
end