Ruby on Rails End of File with SMTP - ruby-on-rails

Question

Apologies if the answer is out there, but in the many similar posts I've browsed, I haven't found the answer I'm looking for.
I've inherited a Ruby on Rails application, and it recently began failing to send emails. From what I can gather, this is due to an smtp failure.
I want to send emails from "do_not_reply#mydomain.com" using "myaccount#gmail.com" for the SMTP settings.
In .../config/environments/production.rb I have
ActionMailer::Base.smtp_settings = {
:enable_starttls_auto => true,
:address => 'smtp.gmail.com',
:port => 587,
:authentication => :plain,
:user_name => '<myaccount#gmail.com>'
:password => '<mygmailpassword>'
}
and in .../app/models/ I have a file called user_notifier.rb which contains
class UserNotifier < ActionMailer::Base
def signup_notification(user)
setup_email(user)
#subject += 'Please activate your new account'
#body[:url] = "<mydomain.com>:8080/activate/#{user.activation_code}"
end
def activation(user)
setup_email(user)
#subject += 'Your account has been activated'
#body[:url] = "<mydomain.com>:8080"
end
def reset_notification(user)
setup_email(user)
#subject += 'Link to reset your password'
#body[:url] = "<mydomain.com>:8080/reset_password/#{user.reset_password_code}"
end
def login_reminder(user)
setup_email(user)
#subject += 'Login Reminder'
#body[:url] = "<mydomain.com>:8080"
end
protected
def setup_email(user)
#recipients = "#{user.email}"
#from = "<do_not_reply#mydomain.com>"
#subject = "<subject>"
#sent_on = Time.now
#body[:user] = user
bcc ["<myaccount#gmail.com>"]
end
end
All of this code once worked, so I'm not sure what has changed. As I write this, I'm realizing that the sudden failure might have corresponded to some maintenance on the network, so I don't know how that might affect things.
EDIT: Added the entire UserNotifier class as requested in the comments

Answer 1

Well, I actually managed to solve this one myself.
I needed to add the :domain option in .../config/environments/production.rb
Why it once worked without :domain I still don't know, but I'll take just having the functional product.
The working setup was
ActionMailer::Base.smtp_settings = {
:enable_starttls_auto => true,
:address => 'smtp.gmail.com',
:port => 587,
:authentication => :plain,
:domain => "gmail.com",
:user_name => '<myaccount#gmail.com>'
:password => '<mygmailpassword>'
}