It takes quite a bit for an email to shock me, but I encountered an exchange yesterday that really surprised me.

A person emailed their cover letter and resume for consideration for employment.

I replied:

Thank you for emailing. All of our positions are currently filled, but I appreciate you reaching out! Have a wonderful week.
Best,
Chasta
To which I received in response(and this is literally all it said):
THANKS FOR NOTHING

In communication, whether we know each other personally or not, it is important  to use professional courtesy!

courtesy