It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
Adds the settings:
raw_email_max_length, raw_rejected_email_max_length, delete_rejected_email_after_days.
These settings control retention of the "raw" emails logs.
raw_email_max_length ensures that if we get incoming email that is huge we will truncate it removing uploads from the raw log.
raw_rejected_email_max_length introduces an even more aggressive truncation for rejected incoming mail.
delete_rejected_email_after_days controls how many days we will keep rejected emails for (default 90)
