So, when a Reddit user asked, 'What's the most professional way you've heard/said, 'screw you,' in the work place?' people were ready to share the funniest or incredibly bold ways they've seen a coworker or employee shut someone down.
Overheard my boss once say 'Our policy is...(long pause while he loads up his phrasing, then clearly changes his mind and just says)...no.' Literally thirty years ago and still gives me a chuckle - Ladybeetus
The f*ck you lawyer letters that I have seen usually start with 'Please be advised' and end with 'govern yourself accordingly.' - catjugglinpimp
'We don't need two weeks notice, you can leave this morning.' - SmarterThanAllOfYou
We have no plans to pursue the matter now or in the future. We ask that you refrain from further contact with us. - penny_can
'As per my previous email'
or
'Let's take this offline'