YAKUMO DELTA X GPS 5 BT Manual page 58

If you use POP3 and you move email messages to a folder you created, the
link is broken between the messages on the Yakumo deltaX 5 BT and their
copies on the mail server. The next time you connect, the mail server sees
that the messages are missing from the Yakumo deltaX 5 BT Inbox and
deletes them from the server. This prevents you from having duplicate
copies of a message, but it also means that you no longer have access to
messages that you move to folders created from anywhere except the
Yakumo deltaX 5 BT.
If you use IMAP4, the folders you create and the email messages you move
are mirrored on the server. Therefore, messages are available to you anytime
you connect to your mail server, whether it is from your Yakumo deltaX 5
BT or desktop computer. This synchronization of folders occurs whenever
you connect to your mail server, create new folders or rename/delete folders
when connected.
For all services except ActiveSync, you can access folder options by tapping
Menu Tools
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in the message list.
Manage Folders