Do you want the arrival time to the mail server or arrival time in Outlook?
The date field used by default is the received time, which is usually the
time the mailbox on the server received it unless the server doesn't
properly add that field. You can try sorting on the last modified time if
you want the time outlook downloaded it - although replying or editing a
message changes the modified time so it's not always accurate.

The received date field is the date your mail server received it unless the
server doesn't stamp it or uses a non-standard format, then it's the date
outlook downloaded it - you should be able to tell which method your account
uses. I believe most accounts use the time it arrived on the server, but I
know a few don't as I had one pop account that used the time I downloaded to
outlook.

the received date is as accurate as your mail server's clock (or outlook)
and no, it can't be spoofed. The send date can be spoofed because the
sending client adds that date although some mail servers replace the sent
time field with the time they actually received it.