> Sure, actually the interceptor sets both attributes to []

I'm not sure what you mean. Can you clarify?

> why is nil expected?

I think I did it that way because it's the default in the Mail gem:

```ruby
mail = Mail.new
=> #<Mail::Message:70179314951880, Multipart: false, Headers: >
irb(main):004:0> mail.cc
=> nil
irb(main):005:0> mail.bcc
=> nil
```

But for the purposes of this change, the `nil` code already works in the staging environments in which this code has been used. So, there should be a compelling reason presented if we want to change it.