VOIP Tech Chat → [Voip.ms] Voip.MS + 3CX... CID question.

My client is using external voicemail for one of their numbers....

We would like to have 3CX forward the original caller's CID when it forwards out to the external voicemail number.

I am sure it's in outbound parameters, but I'm not sure precisely which tags to set.

Assistance would be appreciated.

On the voip.ms side, make sure the trunk is setup as "Asterisk, IP PBX, Gateway or VoIP Switch" and the outbound CallerID Number is blank. That way the caller ID coming from the PBX will be passed through (must be a 10 digit number).
On the 3CX, I am not sure what you have to do since I don't use it

I just installed a 3CX on a windows XP virtual machine to check this then I ran a Wireshark trace.
After about 30 minutes of trying and failing I finally found the key: it appears that it sends the outbound caller ID in the Remote Party ID - Called Party : User Part field and the correct value for the field appears to be OriginatorCallerID

I recently had problems with CID and voip.ms and opened a ticket. Here is a reply I received which may help you or others:

If you are using IP Authentication, we'll use what's in the From Field. If you are using regular username/password authentication, you can pass the CallerID via the "remote-party-id" field. This is for the sub accounts using a PBX or a switch.

For any sub account using an ATA device or softphone directly registered with us, you can use the caller ID field in the sub account settings.