mytreo.net has a great interview with Marc Blank, the author of ChatterEmail. As I’ve mentioned quite a few times Chatter is simply the best email client for the Treo assuming you use IMAP and if your server supported the IDLE command to enable the push effect. Everything is about the change with a pending update. POP3 support is about the be added for everyone still living in mobile dark ages. Unlike other email clients Chatter will continue to support asynchronous functionality with POP just as it does not with IMAP which is a great and significant detail. This means your Treo can manage your mail fully in the background and with the screen off so mail is simply there for when you decide to check.
The new beta with POP3 is coming soon – hopefully within a few days, but probably within a week at the latest.