IMAP Mail not Syncing Across 3 Devices

Hi all

i have IMAP mail set up on MBP, Mini and iPhone 5, all latest software but i appear ot be losing mail. I set up IMAP on all 3 devices, on the OSX devices i have set up Mail and assigned the INBOX, told the SENT, DRAFTS & TRASH to use IMAP but i see that although my MBP appears to get and store all email correctly, the Mini doesnt for some reason. It recieves and holds only 90% of the mail. Where is the rest going?

secondly to this, and i guess this will be solved if i solve the first issue, my iPhone 5 appears to be syncd to the Mini mail, so has the same items missing.

Any ideas? What i can check?

ive read a few posts about assigning folders being a problem but i have done that. Even though i have, in the IMAP folders at the bottom of the Mail sidebar i still have Junk and Sent Messages under my mail heading on both OSX devices, the one that works properly and the one that doesnt. Is that right?