Valid emails save but can't be used for email

Valid emails save but can't be used for email

I have a client with an apostrophe in their email address (X'Yz@someone.com) and it is a valid working email address (I can send from gmail). Zoho CRM let's me save it but won't send to it - says it is invalid. This is a clear bug as this is a legal, valid email address. I also notice that 5 years ago you were asked to fix the same problem so it's been out there a while. Please advise.