Exchange behind AWS ALB Load Balancer with WAF

I'm am trying to configure the following setup:

• AWS ALB load balancer with an Exchange Server as target
• WAFv2 used by the ALB load balancer

I have not added any rule or group rule to WAFv2 yet.

I want to be able to use Outlook Anywhere so I'm trying to see if rpc works in this configuration. When I try...

rpcping /t ncacn_http /s internal.exchange.server.local /o RpcProxy=public.exchange.server.com /P "bobesponja,server.com,*" /H Basic /u NTLM /a connect /F 3 /e 6001

...I get Exception 1722 (0x000006BA).

However, if I detach WAF from the load balancer the rpcping command above is successful.

Is the scenario "Load Balancer+WAFv2+Exchange" not possible/supported by AWS?