How Number Forwards Work
When setting up a call forward, you will need to specify two numbers: the forwarding number, and the forward destination. The carrier currently in possession of the forwarding number (the forwarding carrier) needs to set up the forward. Callers will dial the forwarding number (leg A), and the phone switch responsible for this number will originate a new call to the forward destination (leg B). Once both legs are established, the phone switch will bridge these two calls. Technologically speaking, neither party will know for sure that the call has been forwarded: only the switch, and by extension the forwarding carrier, will be able to see this explicitly. The forwarding switch will proxy all audio and handle the signaling on each leg independently.
The calling party can also dial the forward destination directly. This allows the call to traverse the optimal path along the telephone network. When using a number forward, the call legs may be independently optimized, but under the constraint that all calls must pass through the switch performing the number forward. This often leads to suboptimal call routing, significantly increasing the complexity of the call path and often reducing call quality.
T38Fax does not recommend number forwards as a long-term solution. Number forwards force sub-optimal call routing and significantly increase the complexity of the call path. This generally increases your expenses and also leads to call quality degradation. In other words, expect to see a higher fax failure rate when using a number forward. These are technical limitations present across the telephone network and are not specific to any one carrier. Some voice carriers also discourage call forwarding, but it is especially important for fax.
If you're having trouble with a number forward, the first recommended step is to try to call the forward destination directly. If calls to the forwarding number fail but calls to the forwarding destination succeed, this indicates a problem with the call forward.
Forwarding To T38Fax
Call forwards are invisible to the receiving carrier and endpoint. If you believe a problematic inbound call is being forwarded, please notify the support representative and provide the forwarding number. If this step is omitted, they may not be able to reproduce your problem. Call forwards cost the standard per-minute usage charge plus the standard monthly DID fee for the forward destination number. You will need to contact the carrier currently in possession of the forwarding number to have this set up.
Forwarding From T38Fax To A Third Party Carrier
T38Fax can define many forwarding numbers but only one forwarding destination per trunk. If you need us to set multiple forwarding destinations, you will need to create additional trunks with us: one for each forwarding destination. Each will incur the usual trunk fee. You may also be able to set up such forwarding on your phone system, if you are passing calls through one. Additionally, your usage charge rate will change. We double charge for forwarded calls: once for the inbound call leg, and once for the outbound call leg. Note that the third party carrier handling the forwarding destination may issue a usage charge for these calls as well: contact your third party carrier for more information. Please contact support to set up call forwarding from T38Fax.
Forwarding and Porting
Porting a number is the preferred long term alternative to number forwarding. This moves a number from one carrier to another, so all calls to that number are direct. You can learn more about the porting process here. The port-in process may take a while, so in the meantime you can have the losing carrier forward the number you would like to port to a temporary T38Fax number and request a caller ID change on your trunk from T38Fax support.