Hi,
you are right if the event is not shown in the All Event, Email will not be sent. Now there are couple of steps that you have to try:
1) ESXi Image (From HP or Plain Vanilla ESXi), if it is directly from VMware you have to check for teh Providers on ESXi.
esxcli software vib list | grep hp-smx
Providers are must for getting Indication (WMI Mapper plays no role in case of ESXi, it is only for Managing Windows Box).
Get the providers and install them.
2) ReIdentify first after installing the providers. If already installed Go to -> option -> Subscribe WBEM indication
you can use CLI mxwbemsub to do the same.
3) Now After WBEM Subscription Successful, try the Test again.