######controller#####


  def create
    @user = User.new(params[:user])
    @user.password=newpass()
      if @user.save
      flash[:notice] = 'User was successfully created.'
      email=RegistrationMailer.create_confirm(@user)
      email.set_content_type("text/html")
      RegistrationMailer.deliver(email)
      redirect_to :action => 'login'
    else
      render :action => 'new'
    end
  end

###### mailer class#####


class RegistrationMailer < ActionMailer::Base

  def confirm(sent_at = Time.now)
    @subject    = 'registration'
    @body["user"] = @user
    @recipients = @mail
    @from       = 'noreply@me.org'
    @sent_on    = sent_at
  end
end


######mailer view#####


<%= @user.name %>,

Thank you for registering...



#####error#####

You have a nil object when you didn't expect it!
The error occured while evaluating nil.name

Extracted source (around line #1):

1: <%= @user.name %>,
2:
3: Thank you for registering