fix: Missing space before evelope field of body structure

imap/structure.go

@@ -91,6 +91,8 @@ func singlePartStructure(section *rfc822.Section, fields *paramList, writer *dua
 			return err
 		}
 
+		writer.writeByte(' ')
+
 		if err := envelope(header, fields, writer); err != nil {
 			return err
 		}

imap/structure_test.go

@@ -25,3 +25,51 @@ func TestHeaderOutOfBounds(t *testing.T) {
 	require.NoError(t, err)
 	require.NotNil(t, parsed)
 }
+
+func TestStructureWithRFC822Embedded(t *testing.T) {
+	const message = `Content-Type: multipart/mixed;
+ boundary=dcd8fbdd2e8a8f95ac2024a5a57b37e2c24da4f0a0006ae059da17cb0e5b
+Return-Path: <[email protected]>
+X-Original-To: [email protected]
+Delivered-To: [email protected]
+References: <>
+Subject: Fwd: ISO-8859-1
+To: [email protected]
+From: BQA <[email protected]>
+X-Forwarded-Message-Id: <>
+Message-Id: <[email protected]>
+Date: Wed, 2 Jun 2021 14:18:56 +0200
+User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101
+ Thunderbird/78.10.2
+Mime-Version: 1.0
+In-Reply-To: <>
+Content-Language: en-US
+
+--dcd8fbdd2e8a8f95ac2024a5a57b37e2c24da4f0a0006ae059da17cb0e5b
+Content-Transfer-Encoding: quoted-printable
+Content-Type: text/plain; charset=utf-8
+
+what
+
+
+--dcd8fbdd2e8a8f95ac2024a5a57b37e2c24da4f0a0006ae059da17cb0e5b
+Content-Disposition: attachment; filename=ISO-8859-1.eml
+Content-Type: message/rfc822; name=ISO-8859-1.eml
+
+From: [email protected]
+To: [email protected]
+Content-Type: text/plain; charset=iso-8859-1
+Subject: ISO-8859-1
+
+hey there bro
+
+--dcd8fbdd2e8a8f95ac2024a5a57b37e2c24da4f0a0006ae059da17cb0e5b--
+`
+
+	parsed, err := NewParsedMessage([]byte(message))
+	require.NoError(t, err)
+	require.NotNil(t, parsed)
+
+	expected := "((\"text\" \"plain\" (\"charset\" \"utf-8\") NIL NIL \"quoted-printable\" 6 2)(\"message\" \"rfc822\" (\"name\" \"ISO-8859-1.eml\") NIL NIL NIL 127 (NIL \"ISO-8859-1\" ((NIL NIL \"random-mail\" \"pm.me\")) ((NIL NIL \"random-mail\" \"pm.me\")) ((NIL NIL \"random-mail\" \"pm.me\")) ((NIL NIL \"random-mail2\" \"pm.me\")) NIL NIL NIL NIL)(\"text\" \"plain\" (\"charset\" \"iso-8859-1\") NIL NIL NIL 14 1) 6) \"mixed\")"
+	require.Equal(t, expected, parsed.Body)
+}