is you account IMAP or POP. I would guess IMAP and you are not aware your providers retention policy applies to the local IMAP account. But that is a guess.

Hmmm. Nope. Don't know. It didn't seem to matter using Win7 on my old computer. I had hundreds in the Inbox at one point and didn't lose any. Will check this out though. Thanks for your reply.

Depending on how you "moved" to your new computer you old may have been a pop account and the new an IMAP one. Folk think of email as this homogeneous blob but it is actually a collection of protocols and standards and your choices when setting the program up on your computer make huge differences.