correct way to search for only PDF attachments

[Xu Wang]

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