ACS Release 4 increased the dial plan to 48 stations, 10 through 57. Previously (R3 and down to 1.1) capacity was 40 stations, 10 through 49.

When you assign a guest mailbox in Partner Messaging, you should set the phone status as "No Phone". The auto attendant will know NOT to transfer the call to the phone system, and await the VMS coverage to bring the call back to the mailbox, but instead go straight to the mailbox. You have the phone status set to "With a Phone", the call is sent from the AA to the ACS, and the ACS can't take that extension number.

You also can't take a live call and transfer it to a mailbox above 49 directly - you have to transfer the call to 777, wait on the line for the voicemail to answer, dial *8 and the mailbox number, then hang up to complete the transfer.

Thank you TTT, so if I am hearing your correctly, the ACS R3 working with the Partner Messaging R7 cannot have mailboxes higher than mailbox 50? Then I am confused, When you read in the specs about the Partner Messaging R7 it says 200 mailboxes. I'm assuming they mean 40 extensions each with a mailbox. (012, 012, 8, and 8), then the remaining 160 are considered guest mailboxes?

You can have up to 200 mailboxes on the Partner Messaging.
You can have up to 40 extensions on the ACS (48 for R4 and higher)
Each of the 40 extensions on the ACS can have Auto VMS Coverage enabled, so an unanswered call at the extension can cover to its mailbox.
For mailboxes numbered 50 and above, you can't have a physical extension, so you must create them "without a phone"
To achieve more than 80 mailboxes, you have to set the maximum extension length greater than 2.

For instance, we has a real estate agent that wanted to create informational mailboxes for properties. Set the maximum extension length to 3. The extensions in the office were 10 through 25. The informational mailboxes were 200 through 299. Selector Codes 1 and 2 are Direct Extension Transfer, meaning the 1st digit of an extension number. If you dialed a 2-digit extension number from the AA, it waited an extra 2 seconds to see if you were going to dial a 3rd digit, and then transferred. Dial 3 digits and you get there right away.

Internally, with a live call, you can press VM Transfer (Feature 14) and dial a 2-digit extension number that falls withing the ACS's dial plan to send a call to a mailbox. Outside of the dial plan, you transfer to 777, the VM login prompt. When prompted to login to your mailbox, you press *8 for Transfer, dial the mailbox number that is outside of the dial plan, and since the mailbox was created without a phone, the Partner Messaging knows to go directly to the mailbox. Hang up when the mailbox answers so the caller can leave their message.

The selector codes for AA #3 were turned off for codes 5, 6, 7, and 8. That is why it was not letting me dial mailbox 50. I should have checked that earlier.

TTT thank you for the help.