Dont know if this helps or applies here, but:
There was a time in Germany, when t-mobile sold blackberries, which where locked to the BIS network, because in the Device the Address, to BB connects to, was hardcoded to a t-mobile Server.
Those devices were unable to use a BES server even, with a correctly provisioned Sim-Card.
I thought, that with the apperance of the 9000 Series T-mobile stopped this, but, that may vary by country.
Do you have another BB which can talk to your BES server ? Compare the Values which are in the options, advanced options, HRT table to those, which are listed in your 9300.
If there is anything else then the APN "blackberry.net" in the bold printed Entry, then, the 9300 might be unable to use your BES.
Also, examine the logs of your BES, about every minutes there should be something in the logs which relates to the communication with your 9300. If you send a message from the 9300 to someone, this entry will be logged, if it arrives at the BES.
Example from the magt log:
Code:
[40700] (10/17 11:26:29.306):{0x2D94} {someone@domain.com} Receiving packet from device, size=158, TransactionId=1030180723, Tag=239715, content type=CMIME, cmd=0x3
[30112] (10/17 11:26:29.306):{0x2D94} {someone@domain.com} Receiving message from device, RefId=1501594147, Tag=239715, TransactionId=1030180723, Date=17.10.2010 11:26:34
[40292] (10/17 11:26:29.400):{0x2D94} {someone@domain.com} Email message sent for device, Tag=239715
[40279] (10/17 11:26:29.400):{0x2D94} {someone@domain.com} SubmitToRelaySendQ, Tag=239715
[40000] (10/17 11:26:29.400):{0x764} [BIPP] Send status DATA_ACCEPTED, Tag=239715
[40423] (10/17 11:26:31.212):{0x2C58} {someone@domain.com} Queuing new mail through notification (external). EntryId=458536
[40724] (10/17 11:26:31.212):{0x1AE0} {someone@domain.com} Get record key for this MAPI object, EntryId=458536
[40435] (10/17 11:26:31.212):{0x1AE0} {someone@domain.com} Queuing new mail through notification. EntryId=458536. Msgs Pending 0
[40726] (10/17 11:26:31.212):{0x1AE0} {someone@domain.com} CheckForeignRIMProps - New message with RIM properties detected, deleting RIM properties. RefId=1501594147, EntryId=458536