X-Mozilla-Draft-Info: internal/draft; vcard=0; receipt=0; DSN=1; uuencode=0;
 attachmentreminder=0; deliveryformat=0
From: Invalid User <from_A@foo.invalid>
To: =?UTF-8?B?RnLDqcOpZGxlLCBUZXN0?= <to_A@foo.invalid>
Subject: Test DSN
Message-ID: <f30c39e6-b14b-405a-8bf7-2ccc81fd1f6f@foo.invalid>

Hello world!