Messages missing from Inbox

I have just made the change from pc to iMac, and have a problem with "Mail". I receive some emails, which go to my Inbox. I read them. Then I close "Mail" and do something else. When I reopen Mail, my Inbox is empty: the messages have disappeared. Any messages in "Sent" stay there. What's happening, and how can I stop my messages disappearing?

I have just made the change from pc to iMac, and have a problem with "Mail". I receive some emails, which go to my Inbox. I read them. Then I close "Mail" and do something else. When I reopen Mail, my Inbox is empty: the messages have disappeared. Any messages in "Sent" stay there. What's happening, and how can I stop my messages disappearing? Both Applecare and BT Internet helplines are stumped...each are blaming the other.

Which ISP are you using for Mail? And, is your email setup as POP or IMAP?

My ISP is BTinternet.com; my Incoming Mail Server is imap.mail.yahoo.com. Does that answer your question? Sorry - I'm a novice at this...

I'm not sure how Yahoo handles IMAP but it could be that once the messages are read they're removed. Can you access your Yahoo IMAP account on line and check to see if your email messages are still there on the server?

I know with my GMail account I can do the same but prefer rather to leave messages intact even after being read.

Also, make sure you open your Mail preferences and check "Accounts", "Mailbox Behaviors" and "Advanced" tabs to see if the options are set correctly.

Check your trash in mail and see if they are there.

@Hoverstop

Please do not cross post. Post only to one forum and reply back to the same thread. I moved your cross post here and merged it where it belongs.