rails actionmailer error with 'part' method - ruby-on-rails-3

Question

I'm upgrading rails 2.3.2 app ot rails 3.
Have unknown error with sending email message in MailerFormError.
MailerFormError is my model: class MailerFormError < ActionMailer::Base
At 1st I have error with 'deliver_send' method (undefined method `deliver_sent' for MailerFormError:Class),
I change it to 'send'. Now I have this:
NoMethodError in LeadsController#create
undefined method `part' for #
My code in controller:
#msg = {}
#msg["errors"] = #lead.errors
#msg["params"] = params
#MailerFormError.deliver_sent(#msg)
MailerFormError.sent(#msg)
This is my class with sending method:
def sent(msg, sent_at = Time.now)
#subject = ("Ошибка при заполнении формы").force_encoding('iso-8859-1').encode('utf-8')
#recipients = 'mymail#gmail.com'
#from = 'mymail#gmail.com'
#sent_on = sent_at
#headers = {}
part( :content_type => "multipart/alternative" ) do |p|
p.part :content_type => "text/plain",
:body => render_message("sent.plain.erb", :msg=>msg )
end
end

Answer 1

1) for Rails 3, to send your notification in your controller , you have to write this :
MailerFormError.sent(#msg).deliver
2) And you have to rewrite your 'sent' method in the Rails 3 way :
def sent(msg, sent_at = Time.now)
...
mail(:to => '...', :from => '...', :subject => '...') do |format|
format.html
format.text
end
...
end
You can also create the text version and html in your view directory app/views/mail_form_error : sent.text.erb and sent.html.erb