We can also check and modify the attachment settings with the help of MAPI properties of the message and more specific the attachment table in order to see if you really have an attachment for this message.

1. Open MFCMAPI and click on Session and click Logon.

2. After that select the profile and double click on the primary user mailbox.

3. New window will get opened and you need to expand the root mailbox and select IPM_SUBTREE and open the Inbox folder.

4. Once you click on Inbox then select the mail message which have attachment included and you will see the option on the bottom of the window with the property value : PR_ATTACHMENT_HIDDEN

a) Select folder that contains your message with the attachment.

b) Select the message that normally has an attachment and right click on it in order to choose the Display Attachment Table option (next to this option you have also the Display Recipient Table if you want to check the recipient list for a message)

c) A new window will open (Attachments)

d) Normally if your message contains an attachment you will see it in the upper panel

e) What you should do next is to select the attachment and check in the lower pane the MAPI properties

f) Then you need to check the following property: PR_ATTACHMENT_HIDDEN. In my case I can see that the value of this MAPI property is: True.

g) This might explain why I cannot see the attachment in Outlook.

h) Then you will need to modify change the value of this property to False in order to see if this will able to solve my problem.

i) Then you need to double click on this property and the Property Editor window will appear

j) Then you need to uncheck the Boolean checkbox and click OK

l) Next, in order to save the changes for the message, You will need to select the Actions menu and click on Save Changes On Message option

m) You will see that the value changed to False for the PR_ATTACHMENT_HIDDEN 5. Let’s check now in Outlook if we can see correctly the attachment when opening the message. The attachment appears correctly now.

Further more details please refer to the below mentioned article link :