Hello @contoured
Please note that currently there is no report that can track whether or not a user has recorded a custom voicemail greeting. Other users however have created scripts that can check the folders of extensions and check for custom greeting messages. When a user records a new greeting message, that message is saved in the folder under "C:\ProgramData\3CX\Instance1\Data\Ivr\Voicemail\Data\EXT_Number ".
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.