Try this filter
"@SQL=(""urn:schemas:httpmail:subject"" LIKE '%test message for extraction%') AND ([ReceivedTime] >= '" + DateTime.Now.AddHours(-1).ToString("yyyy-MM-dd HH:mm") + "')"
Try this filter
"@SQL=(""urn:schemas:httpmail:subject"" LIKE '%test message for extraction%') AND ([ReceivedTime] >= '" + DateTime.Now.AddHours(-1).ToString("yyyy-MM-dd HH:mm") + "')"