Open Messaging
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Select Options > Settings > E-mail > Mailboxes. Select a mailbox and 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 IMAP4 mailbox 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.