Use heredocs.

spec/fixtures/emails/iphone_signature.eml

-Delivered-To: test@mail.com
-Return-Path: <walter.white@googlemail.com>
-From: Walter White <walter.white@googlemail.com>
-Content-Type: multipart/alternative;
-  boundary=Apple-Mail-8E182EEF-9DBC-41DE-A593-DF2E5EBD3975
-Content-Transfer-Encoding: 7bit
-Mime-Version: 1.0 (1.0)
-Subject: Re: Signature in email replies!
-Date: Thu, 23 Oct 2014 14:43:49 +0530
-References: <1234@mail.gmail.com>
-In-Reply-To: <1234@mail.gmail.com>
-To: Arpit Jalan <test@mail.com>
-X-Mailer: iPhone Mail (12A405)
-
-
---Apple-Mail-8E182EEF-9DBC-41DE-A593-DF2E5EBD3975
-Content-Type: text/plain;
-  charset=us-ascii
-Content-Transfer-Encoding: 7bit
-
-This post should not include signature.
-
-Sent from my iPhone
-
-> On 23-Oct-2014, at 9:45 am, Arpit Jalan <test@mail.com> wrote:
->
-> Signature in email replies!
-
---Apple-Mail-8E182EEF-9DBC-41DE-A593-DF2E5EBD3975