Jim,
Pls select Tool>Option>General (Tab)>Send/Receive mail;
To toggle the values in the field to your desired value (5 minutes, if u
like), this field will check for new mails at a interval you just
specified.
That is all i knew, maybe there better alternatives someone will show you
later.
PS Mine is a Chinese version, the words used here may not be the exect
equivalent in English version.
good luck
mingman