Apostrophes messed up in epub emailed to Kindle

I’ve never really sent any epubs to my Kindle before so thought I’d try it today.

I sent two or three epubs via email and when these came through to my Kindle all of the apostrophes and a number of other characters had seemingly been replaced with random strange characters. It seemed to be mainly apostrophes that were messed up.

Is there any way to fix this so that they appear properly? I’d also be interested to know why this happens - is there something in the source epub file that doesn’t pass through the Kindle conversion process correctly?

Many thanks.