ActionMailer Problem

Hi,
I wanted to send an attachment in mail.
for testing , I have send png image attachement in mail. Mail delivery
is
completely working but the attachment in that mail show file name as
“nonname”
what should i do??
My code is:

class SendMail < ActionMailer::Base
default :from => “[email protected]

def welcome
attachments[“adfd.txt”] =
File.read("#{Rails.root}/public/images/f.txt")

 mail(:to => "[email protected]",
      :subject => "welcome mail").deliver

end

end