Hi, I would look to look for all emails from a colleague jongho. I tried: from:jongho attachment:pdf which seems to do as I wanted. To understand more, what does the following search for? from:jongho attachment:.*pdf I know it is incorrect as the results tell me, but what exactly does it do? Also, how does the first one above know that I want only PDF attachments and not an attachment called "pdformula.txt" ? Kind regards, Xu