Open Messaging
and select Options > Settings > E-mail > Mailboxes. Open a mailbox. Select Retrieval settings > Retrieval amount.
To specify the number of e-mail messages to retrieve automatically or when you connect to a remote mailbox, select from the following:
For the IMAP4Mailbox type you can select different retrieval amounts for Inbox and other mailbox folders to which you have subscribed.
If you use automatic retrieval of new e-mail messages,All is the default value for this setting.
To save your settings, select Back.