Automated notification to mirrored person column

Hi, I have a holiday/vacation tracker that pulls through the holiday requestors manager via a mirrored board column automatically. I need the manager to be notified of the new holiday request when it is created for them to approve. I’ve tried to do this via gmail integration but unable to select the manager (mirrored column) as the recipient. Is there any other way I can notify the manager (mirrored column) when a new item is created?