New Post: message.Attachments sometimes is wrong

Hi,

sometimes, the message.Attachment.Count is zero even if there are attachments.
Here is the log (I've changed the mail addresses manually):

IMAPX24 UID FETCH 368 (FLAGS BODYSTRUCTURE)

* 339 FETCH (FLAGS (\Answered) BODYSTRUCTURE ((("TEXT" "PLAIN" ("charset" "iso-8859-1") NIL NIL "quoted-printable" 1563 33 NIL ("inline" NIL))("APPLICATION" "XML" ("name" "daticert.xml") NIL NIL "base64" 1236 NIL ("inline" ("filename" "daticert.xml")))("MESSAGE" "RFC822" ("name" "postacert.eml") NIL NIL "7BIT" 919 ("Thu, 23 Jan 2014 15:59:24 +0100" "prova - PECID=2964" ((NIL NIL "mario.rossi" "postecert.it")) ((NIL NIL "mario.rossi" "postecert.it")) ((NIL NIL "mario.rossi" "postecert.it")) ((NIL NIL "pinco.pallo" "pec.ording.roma.it")) NIL NIL NIL "<E685AED3.00243072.BF9CEA08.0B946E84.posta-certificata@postecert.it>") ("TEXT" "PLAIN" ("charset" "iso-8859-1") NIL NIL "7bit" 7 1) 21 NIL ("attachment" ("filename" "postacert.eml"))) "MIXED" ("boundary" "----------=_1390489180-9987-7"))("APPLICATION" "X-PKCS7-SIGNATURE" ("name" "smime.p7s") NIL NIL "base64" 3412 NIL ("attachment" ("filename" "smime.p7s"))) "SIGNED" ("protocol" "application/x-pkcs7-signature" "micalg" "sha1" "boundary
" "----F66FF9B4EFA24E0CC07B434906A082AE")) UID 368)
IMAPX24 OK FETCH complete

A first chance exception of type 'System.FormatException' occurred in System.dll

The attachment are:
smime.p7s
daticert.xml
postacert.eml

please note that I've performed some modifications to the source code because of some "infinite loops" (see my previus discussion)

It happens only sometimes... but I've not yet identified the cause.
How is it possible ? Of course, I can access to the attachment accessing the webmail site
thanks in advance
Francesco