IMAP will not show newest e-mail.

Question

When I check Mail with IMAP the iPhone downloads all messages but doesn't seem to display the newest first! ???
I am helping two users set up their iPhones and they both check mail from the same server just different accounts.
IMAP -- When I set them up to check via IMAP they can't see the newest messages on their phones. They each have about 500 e-mails in their inbox but all they really need to see are the most recent ones.
POP -- When I connect them via POP they can't open attachments or it takes a TREMENDOUS amount of time. I keep getting =_NextPart and some numbers in the place of my mail or attachment.

Answer 1

Well that narrows it down now that I know it's not the iPhone necessarily but the order in which my IMAP server pushes the e-mails.
When the iPhone (or any other client) requests mail, the server seems to send random e-mails to the client until the request is fully completed. I've noticed that the iPhone will get mail in splurges. 150 here 6 there another 50. etc. I have to hit update serveral times to get it to see all of the mail, even then it sorts really strangely. It's like it receives messages -> parses 25 of them at a time -> sorts and displays those 25. So even though in the background it's "seeing" that there's more e-mail on the server it will only sort the first 25 it received.
The workaround so far has been to use POP e-mail which is frustrating as well.
When I use POP I'm having trouble with the phone taking crazy amounts of time to render an e-mail or attachment. (particularly those with excel attachments). On the SAME EXACT e-mail sometimes it will pop right up, other times it will take hours. I can't be sure if it's still downloading the message/attachment either because normally when you touch a large attachment it will show you the progress as it's being downloaded. This issue happens after that point with the little swirly showing you the item is being loaded.
The really strange part is the e-mails and messages this happens to don't correlate in size at all. Last one liner message with a 15k excel attachment took 5 hours to open. (all in the same try.) Later I used the same e-mail as a benchmark and tried opening it over and over. Sometimes it would open right away, sometimes it would take 10 minutes or more (didn't want to wait hours though).
The bottom line is this is happening too often. If it was once in awhile it wouldn't be worth complaining about, but this coupled with IMAP handling issues are starting to pick at me.
Would it be worth my while to have all e-mail forwarded to another account that the iPhone could check exclusively. Say a .mac account? Do these phones come with .mac accounts?
I'm starting to run out of ideas.