BlueMail supports both IMAP and POP3, however, we recommend using IMAP over POP3, where possible, as it is a modern protocol which supports, folder sync, delete on server sync between devices, push notification and many other benefits. IMAP by design keeps all devices in sync.

Please note, if you do use POP3 for your given accounts on multiple devices (such as your mobile or PC), one of the devices may download the emails from your server and remove it (depending on your server settings).