SE is still a small site with about 130 members and not much applications to look over.
However, with such a small site I think it's possible to add "Automatic Rejection Letters" attached to the club linked with the job you're applying to. Like you do with applications to the Quidditch-teams.
To apply for a job you send an email and also apply to join the respective Club. For example The Teachers Club.
In this club, there's an option to write automatic Rejection Letters which you write one time.
For example "Sorry, you have not been hired. Better luck next time, best regards Principal X" or something similar. (No reasons needed)
If you're not hired, the one hiring just needs to press the red X-button in the club for an automatic owl to be sent to the one who applied and got rejected.
For bigger sites like EU I know this might not be possible due to more applications, but for smaller sites, for example, SE (with about 130 active members) this is a possibility and would relieve a lot of anxiety both for members and staff who gets bombarded with owls.
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