Is there a way to tell the difference between an attached file, and an image that is embedded in an email?

Question

When Outlook receives an email, it appears that attached files and embedded images are carried as Attachments.  In looking at emails and the individual attachments/embedded images with Outlook Spy, I do not see anything that would tell me which is
which.  Obviously Outlook knows the difference ... is there something that I'm missing?mdpowers

Answer 1

Hi Ken,
In my code i have something like that:
public static bool IsEmbeddedAttachment(Outlook.Attachment attachment)
//Anexos que não são embedded são obrigatóriamente olByValue, porém os embedded podem ser de qualquer tipo
if (attachment.Type != Outlook.OlAttachmentType.olByValue)
return true;
//Busca a propriedade contentID do anexo. Anexos embedded não precisam necessáriamente gerar um ContentID. Anexos fixos não geram ContentID
string strATTACH_CONTENT_ID = attachment.PropertyAccessor.GetProperty(@"http://schemas.microsoft.com/mapi/proptag/0x3712001E").ToString();
//Busca a propriedade contentLocation. Para que o anexo seja embedded é necessario que essa propriedade esteja vazia ou nulla
string strATTACH_CONTENT_LOCATION = attachment.PropertyAccessor.GetProperty(@"http://schemas.microsoft.com/mapi/proptag/0x3713001E").ToString();
if (!string.IsNullOrWhiteSpace(strATTACH_CONTENT_ID) || !string.IsNullOrWhiteSpace(strATTACH_CONTENT_LOCATION))
//Busca a propriedade AttachFlag se for diferente de 4 é uma imagem embedded
if ((int)attachment.PropertyAccessor.GetProperty(@"http://schemas.microsoft.com/mapi/proptag/0x37140003") == 4)
return true;
if ((int)attachment.PropertyAccessor.GetProperty(@"http://schemas.microsoft.com/mapi/proptag/0x37050003") == 6)
return true;
if ((int)attachment.PropertyAccessor.GetProperty(@"http://schemas.microsoft.com/mapi/proptag/0x37140003") == 4)
return true;
return false;
And was working very well until last week. 
I have a problem with a single email. This email attachments possess 2 PDF type files. These files are not embbed in the email, but they have the contentId property. Could you tell me why? or if its possible discovery why this happens?
PS.: Sorry about my english.
Att's,
Anderson Rissardi.