emails in Imac

Hi Guys
My first Imac - really fast but a few anomalies to sort out compared to windows.
It seems as though as soon as I have read my emails when I reopen the email folder they are all in the trash folder - I dont want that - Ive tried moving them back into Inbox but when I reopen the mail, guess what they're back in the trash folder.
I really want them to stay in inbox for ever unless I delete them. What do I do to correct this?
Thanks for your help & patience:Confused

That's not a setting in Mail unless you have made up a rule. Are you sure that you have not selected to delete messages that have been read from your ISP options? Access your ISP on the Web and check to see what options are selected.

Also, you really don't want received mail to remain in your InBox. Create folders (Mailboxes) beneath your InBox to store those messages that you read and wish to keep. You do that by right clicking on the mailbox area and select new Mailbox.