Received: (Postfix, from userid 1000); Mon, 4 Dec 2006 14:51:39 +0100 (CET)
From: Test Sender <sender@testrun.org>
Subject: Large image test
To: alice@example.org
Message-ID: <big-image-test@testrun.org>
Date: Thu, 17 Dec 2020 15:38:45 +0100
User-Agent: Test-Agent/1.0
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="------------BIG_IMAGE_BOUNDARY"
Content-Language: en-US

This is a multi-part message in MIME format.
--------------BIG_IMAGE_BOUNDARY
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit

Here is a 4k image

--------------BIG_IMAGE_BOUNDARY
Content-Type: image/png;
 name="4k_image.png"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="4k_image.png"

iVBORw0KGgoAAAANSUhEUgAADwAAAAhwCAIAAAAf3FwlAAAAEElEQVR4nAEFAPr/AP////8AAAAFCeiupAAAAABJRU5ErkJggg==
--------------BIG_IMAGE_BOUNDARY--