a little question,

Bes push mail from mail server to handhelds but what's the way of the mail from the handheld to the user mail box ?
Via the 3101 port on the firewall or via smtp ?

tx

the handhelds do not really send mail. They just instruct your server to.

ok but how ?
is the 3101 port on the firewall always open by BES ?

From the BES 4.0 Exchange Features and Technical Overview PDF (available free on the BlackBerry support website):

Email sent from a handheld

1. Message is sent from handheld: The user sends a message from the handheld. On the handheld, the message is assigned the RefId. If the message is a meeting invitation or calendar item, the handheld appends the calendar information to the message.

2. Compresses and encrypts: The handheld compresses and encrypts the entire message.

3. Sends to the BlackBerry Enterprise Server: The message is sent to port 3101 over the wireless network to the BlackBerry Enterprise Server.

4. Decrypts and decompresses: The BlackBerry Dispatcher uses the user encryption key to decrypt and decompress the message. If the message cannot be decrypted using the unique encryption key, the BlackBerry Enterprise Server ignores the message and sends an error to the handheld.

5. Delivers to mailbox: The Messaging Agent places the message in the user’s Microsoft Exchange mailbox.

6. Copied in Sent folder: The Messaging Agent places a copy of the message in the Sent Items folder in the desktop email program. This step does not take place if the Don't save a copy to the Sent Items folder option is enabled in the user settings and that setting is permitted on the BlackBerry Enterprise Server.

7. Routes to recipients: The Microsoft Exchange Server routes the message to the recipients. As a result, a message that is sent from the handheld is the same as a message that is sent from the desktop; messages originate from the user corporate email address, and, if necessary, a copy is placed in the Sent Items folder.