Does "Should" mean "if"?

[Hlearner]

"Should you have any questions, please feel free to contact us"

I frequently see this sentence in end of emails and I wonder what "should" means here and basically in what another kind of similar format I can use "should" and does it mean if?

I guess it is more polite(?) than this form: " If you have any question...".

Please give me some explanation to clear it.

Thanks

[Beeesneees]

Yes, it's considered more polite than 'if you have...'
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Cheers m' dears!

[Mordant]

I really don't detect any difference in politeness. Maybe it's a British thing.