Action Mailer not executing Proc to generate TO field - ruby-on-rails-4

Question

UP 04/08/2015 : Is it actually possible to use both .deliver_later and a proc ?
My problem :
My email doesn't execute the procedure to generate the TO field, thus sending a bad email on postfix
Postfix log
sudo tail -n 150 /var/log/mail.log
Jul 30 17:39:44 je postfix/pickup[3974]: 0DA531FC2AFA: uid=1030 from=<candidature#myorg.com>
Jul 30 17:39:44 je postfix/cleanup[8430]: 0DA531FC2AFA: message-id=<55ba453fc4fd1_20e02375a9c04882a#myorg.mail>
Jul 30 17:39:44 je postfix/qmgr[3506]: 0DA531FC2AFA: from=<candidature#telecom-etude.com>, size=18915, nrcpt=2 (queue active)
Jul 30 17:39:44 je postfix/error[8522]: 0DA531FC2AFA: to=<Proc:0xbbd2989c#/var/www/intranet_rails_production/releases/20150729170507/app/mailers/mailing_lists_mailer.rb:42>, relay=none, delay=0.41, delays=0.22/0.02/0/0.17, dsn=5.1.3, status=bounced (bad address syntax)
Jul 30 17:39:44 je postfix/error[8522]: 0DA531FC2AFA: to=<#<Proc:0xbbd2989c#/var/www/intranet_rails_production/releases/20150729170507/app/mailers/mailing_lists_mailer.rb:42>>, relay=none, delay=0.52, delays=0.22/0.02/0/0.28, dsn=5.1.3, status=bounced (bad address syntax)
Controller
...
if Rails.env.production? # Using :sendmail as delivery method
MailingListsMailer.action(#mail).deliver_later
else # Typically using :letter_opener or :file as delivery method
MailingListsMailer.action(#mail).deliver_now
...
Mailer
class MailingListsMailer < ActionMailer::Base
def action(message)
format_mail_params(message)
mail(
to: Proc.new {read_emails_file},
...
)
end
private
def read_emails_file
File.read('emails.txt').split('\n')
end
end
Config
config.action_mailer.delivery_method = :sendmail
config.action_mailer.smtp_settings = {
:address => "localhost",
:domain => "myorg.fr"
}
config.action_mailer.default_url_options = { host: 'myorg.fr', protocol: 'https' }
EDIT : I was using a proc as suggested in the ActionMailer Basics #2.3.3

Answer 1

You probably don't need the Proc wrapper at all, try this:
def action(message)
format_mail_params(message)
mail(
to: read_emails_file,
...
)
end
To debug it, do something like this:
def action(message)
format_mail_params(message)
puts "*"*50
emails = read_emails_file
puts emails
puts "*"*50
mail(
to: emails,
...
)
end
Then check the server logs for the message that looks something like:
*******************************************************************
[...]
*******************************************************************
Iterate the Emails
Because you don't want to divulge everyone's email, and avoid spam detection, you may want to iterate the emails array:
def action(message)
format_mail_params(message)
read_emails_file.each do |email|
mail(
to: email,
...
)
end
end