Error: "Cannot mark the items read or unread."

[MktTrader]

My automation project works except for this stuborn error
message that pops up intermittently.

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Microsoft Outlook
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Cannot mark the items read or unread. The most likely
reasons are:

· You don't have permission to modify the items.
· These folders do not support marking items as read or
unread.
· You did not select anything to mark.
· The server is unavailable.

---------------------------
OK
---------------------------

This one is related to the ReadMail addin used in several
rules for the "Clear the Message Flag" feature and move
the mail. It all seems to process ok, but leaves a stack
of these error messages behind.

How can I get around this?

PS: I searched Google, the Knowledge Base and Slipstick
but found nothing. No Reply to email from ReadMail.