You can either define a mail schedule based on a predefined schedule or define your own custom schedule.
Use the following schedule
Click to define a schedule for sending and receiving e-mail, and then specify an e-mail frequency.
The frequency at which e-mail is sent and received is determined by the following:
E-mail Delivery Method. If you elected to forward all mail to an e-mail server at your Internet service provider (ISP), e-mail delivery will be based on the set schedule.
If you have a broadband connection to the Internet, Exchange sends e-mail immediately regardless of the set e-mail schedule.
E-mail Retrieval Method. If you have a broadband connection to the Internet and your e-mail is delivered directly to Exchange, retrieval of Simple Mail Transfer Protocol (SMTP) mail is not affected by the mail schedule. Retrieval of POP3 (Post Office Protocol 3) mail is instead based on the set mail schedule.
If e-mail from the Internet is held at your ISP until Exchange sends an ETRN or TURN after Authentication signal, e-mail retrieval is based on the set schedule.
Do not change the schedule I have defined
Click if you have defined a schedule in Exchange or if you are rerunning the wizard and want to preserve the current settings for your SmallBusiness SMTP connector.
To define a schedule in Exchange, click Start, click Server Management, right-click SmallBusiness SMTP connector, and then click Properties.
your Exchange server
SmallBusiness SMTP connector
In the SmallBusiness SMTP connector Properties dialog box, click the Delivery Options tab, and then click Customize.
The minimum schedule interval you can set is for every 15 minutes.