OK, thanks to both of you. That's a big help. I didn't
know that pop3 only checks inbox *by definition*
That's the answer to my problem.
Unfortunately, I used to use imap for a brief period
about 3 years ago, but it turned out that my ISP was
offering that for free only on trial. Now, it's for an
extra fee, so I had to revert to pop3. With gmail, I
could try imap again, since I recall liking it, back
when I had tried it on my ISP, but I do not want
important/financial/business/etc mail going through
gmail.
I realize that all email is insecure in transit, but I
would like to believe that at least the servers of my
ISP are trustworthy enough to warrant my confidence
and my business and my loyalty. That's why I pay them.