Email Chunking for SMTP API

user.rb

# This method separates emails into 1000 email chunks for bulk sending
# through an SMTP API such as SendGrid API

  def self.chunk_emails(recipients)
    if recipients.count < 1000
      [recipients]
    else
      split_recipients = recipients.count.divmod(1000)
      # Example, if recipients.count == 3200, then ...
      quotient  = split_recipients[0] # => 3
      remainder = split_recipients[1] # => 200
      chunks    = []
      (1..quotient).to_a.each_with_index do |el, ind|
        starting    = ind * 1000
        ending      = el * 1000
        chunks[ind] = recipients[starting...ending]
      end # This loop gives 1000 email chunks but does not handle any remaining
      chunks[quotient] = recipients[(quotient * 1000)..-1]
      # This line gets the remaining emails
      # (in previous example, this would get the last 200 emails)
      chunks
    end
  end

# REFACTORED TO ONE LINE

  def self.chunk_emails(recipients)
    chunks = recipients.each_slice(1000).to_a
  end

# This would also work (rails only, ruby will not run this method)
# Plus I think it reads better

  def self.chunk_emails(recipients)
    chunks = recipients.in_groups_of(1000, false)
  end

# As far as Benchmarking, after running about 25 tests, there's no clear winner. Each won about half the time. 
# So, I'll stick with m chunk_emails method since it seems to me the most readable.