Yes works 'similar' to masking but it isn't a mask for any particular user. It is just a text entry in the format of an email as required for normal NPrinting operation.
In any case, please check your NPrinting Scheduler log file for a similary entry (the Guids, Email address and NP version will be different):
"Qlik.NPrinting.Repo 184.108.40.206 Qlik.NPrinting.Repo.Service.ReportPublishingService 20191106T153403.089-08:00 INFO QLIKSERVER3 0 0 0 0 0 0 0 0 The e-mail for bucket e4c73704-6c0b-4dcc-877b-2ddae2a00176 has been sent to email@example.com"
The point here is that you don't see any information appended to the front of the email address. It goes out as is and nothing is added by NPrinting.
It would be interesting to see your NP scheduler log entries at the time of your publish task execution.
Hope this helps to clarify...
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