Caller ID showing as [email protected]

So I’ve been running a trial with some users and Cisco 9951 phones. It’s gone well and we’re ready to buy the rest of the handsets, but the 9951 is end-of-life, so I picked up an 8811 to see how that went. It seems fine, so the 8851 is going to be the model of choice.

I did all the config and testing with the 9951 though, so when I switched to the 8811 today to confirm everything still worked, I ran into an issue with caller id.

First, an example with two 9951’s: Extension 101 (john) calls extension 102 (bill). On Johns phone, the display shows ‘Bill Smith’ and below it ‘101’ as would be expected. Bill’s phones shows the same, "John Smith’ and ‘101’.

Call 101 from the 8811 though, and it shows “Bill Smith” and "[email protected]", the display on the destination phone is normal.
Call from a 9951 to the 8811 and the inbound call shows normally too.

So, just on outbound calls from the 8811, the called number is showing as a [email protected] style value.

The asterisk config is not changed. I unplugged the 9951 and plugged in the 8811 configured to the same credentials.

So, it’s something ‘special’ about the 8800 series, I’m hoping there is something I can set in Asterisk/FreePBX to switch the behaviour to the expected. We’re not making SIP calls, if a user dials 101, they don’t expect to see [email protected] on their phone.

I know it’s a bit niche, but I’m hoping someone can help point me toward a solution. I’ve already tried experimenting with trustrpid, sendrpid etc.
Thanks.