Syntax error in BODYSTRUCTURE. Unexpected token: NIL

[neobgd]

When I try to fetch Message summary I got this error:
Syntax error in BODYSTRUCTURE. Unexpected token: NIL

The code which I use is:

var inbox = client.Inbox;
inbox.Open(FolderAccess.ReadOnly);
int index = Math.Max(inbox.Count - a.received_last, 0);
foreach (var summary in inbox.Fetch(index, -1, MessageSummaryItems.UniqueId | MessageSummaryItems.BodyStructure |MessageSummaryItems.Flags)){};

When I remove MessageSummaryItems.BodyStructure everything is fine.
I am using latest version 2.3.1.6

IMAP log is in the attach.
imap.zip

[jstedfast]

The problem is that the Exchange server is sending a bad BODYSTRUCTURE response.

Here's the first occurrence:

S: * 37 FETCH (UID 67 FLAGS (\Seen \Recent) RFC822.SIZE 14801 ENVELOPE ("Tue, 9 Jul 2019 13:53:17 +0200" "Verify your Apple ID email address" (("Apple" NIL "appleid" "id.apple.com")) NIL ((NIL NIL "appleid_usen" "email.apple.com")) ((NIL NIL "milan.tanasic" "evocon.rs")) NIL NIL NIL "<786519723.45280397.1562673197246@email.apple.com>") BODYSTRUCTURE (("text" "plain" ("charset" "ISO-8859-1") NIL NIL "QUOTED-PRINTABLE" 850 31 NIL "inline" NIL NIL)("text" "html" ("charset" "ISO-8859-1") NIL NIL "QUOTED-PRINTABLE" 14692 502 NIL "inline" NIL NIL) "alternative" ("boundary" "----=_Part_45280395_786508794.1562673197246") NIL NIL))

In both the text/plain and the text/html body parts, it is sending "inline" instead of ("inline" NIL):

("text" "plain" ("charset" "ISO-8859-1") NIL NIL "QUOTED-PRINTABLE" 850 31 NIL "inline" NIL NIL)

According to the specs:

body-type-1part = (body-type-basic / body-type-msg / body-type-text)
                  [SP body-ext-1part]
body-type-text  = media-text SP body-fields SP body-fld-lines
body-ext-1part  = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang
                  [SP body-fld-loc *(SP body-extension)]]]
                    ; MUST NOT be returned on non-extensible
                    ; "BODY" fetch
body-fld-dsp    = "(" string SP body-fld-param ")" / nil

The body-fld-dsp syntax is not being satisfied in the response given.