I recently switched an email account from POP to IMAP. At the time I switched, there were 50-60 email messages already on the server. After I switched, I uploaded all of my old, downloaded POP messages from that account to the server, using Mail 4.2 (1078) on Mac OS X 10.6.3 Build 10D573. There were a little over 3000 old messages uploaded. The bug is that after uploading the old messages to the server, I can no longer see the recent (50-60) messages on my iPhone or iPad. I have Mail on the iPhone and iPad set to show the 200 most recent messages. However, Mail seems to think that the older, uploaded messages are more recent than the messages that were already on the server. This is despite the fact that the dates of the messages displayed in Mail are the correct and the same as they were before. I am able to see recent email messages that are received after uploading the old POP messages. It's only the messages that were already on the server that can't be seen in iPhone or iPad Mail. I have no problem in Mac Mail: I can see all the messages recent and old, each one with its correct date. On looking at the IMAP protocol, my guess is that iPhone and iPad Mail are simply getting the message sequence numbers and taking the last 200. However, as far as I can tell, IMAP offers no guarantee that the message sequence is in date order. Indeed, it seems that the only way for Mac Mail to upload the messages to the server is via the IMAP 'append' command, which is documented to put the message at the end of the destination mailbox. Thus, the older POP messages will be at the end of the message sequence after uploading. New messages received via SMTP are also added to the end of the mailbox, which is why I'm able to see them too. To fix this bug, I believe that iPhone and iPad Mail need to look at the actual dates of the messages, not just the sequence numbers.