The email address I use is a personalised Gmail account using my own domain.

I have tried other email addresses, but they are all the same type of account.

It used to work without any issues, but recently it has been stripping the code. I have been having to update the code to get it to work correctly, but it is getting worse. It has now reached the point where I can sometimes send individual emails without this occurring, but when I try to bulk send, it always strips the code.