I believe this is because the apostrophe is used as a quote in some graph queries. So, to use the apostrophe in the API call, you would need to escape it. This is done by adding another apostrophe.
So in your Mendix application, you can use the ReplaceAll function to look for apostrophes, and if found, add another one next to it. Mendix also needs apostrophes to be doubled, so assuming the email address is in a variable called $vEmail, the following should work.
replaceAll($vEmail, '''','''''')
https://docs.mendix.com/refguide/string-function-calls/#replaceAll
I hope this helps.