I would recommend double checking that you have the right office version installed.

I tried your exact automation and it works for me.  In searching for that error message in Google I found this article - https://stackoverflow.com/questions/4656360/unable-to-cast-com-object-microsoft-outlook-c-sharp.  This indicates that you might have encountered something other than a MailItem - I would put a Try .. Catch around the steps from your loop and see if it this happens all the time or only for specific items.

As of now, no available solution.

Finally i use C# code to search emails.

This helps you

https://stackoverflow.com/questions/4656360/unable-to-cast-com-object-microsoft-outlook-c-sharp

I have tried to get the count of the e-mails in a folder using method RetrieveEmail of MS Outlook Connector and getting the same error discussed above (Unable to cast COM object)

Below are the steps followed

Step 1: Success
Folder: Draft (Low in Volume and no sub-folders present)
Read Type: Unread
O/P: Count of emails retrieved

Step 2: Failure
Folder: Inbox(High in Volume and various sub-folders present)
Read Type: Unread
O/P: Error received(Unable to cast COM object)

Step 3: Failure
Folder: Draft (Low in Volume and no sub-folders present)
Read Type: All
O/P: Same error encountered

Deleted the RetrieveEmail automation block and applied the new automation block in same manner.

Step 4: Success
Folder: Draft (Low in Volume and no sub-folders present)
Read Type: All
O/P: Count of e-mail retrieved

For Inbox it is giving error consistently. Is it related to volume of the email present. However, I have tried with 2-3 sub-folders of Inbox as well which has low volume but still giving same error.
Automation code for each step is in attachment. Please suggest how to solve this error.

Anyone can help on this issue? Not only myself, but also others such as Manish above encounter the same issue.

This needs an SR.

@WoodYang,

Please let us know the SR ID when you open it so that we may track for you!

Thanks!