What might cause this IMAP client error - "'Unexpected: Non-last response line..."

[edwinyzh]

The error happens during the execution of TidImap4.UIDRetrievePeek, any hint as to trace the source of the issue?

And here is the full error message:
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Debugger Exception Notification
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Project program1.exe raised exception class EIdReplyIMAP4Error with message 'Unexpected: Non-last response line (i.e. a data line) did not start with a *, offending line: nthalten. Sollten Sie diese E-Mail irrt=C3=BCml='.
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Thanks.