Typically MIME.The format of email attachments sent from FBSD to Win 10 is largely unreadable.
Language has very little to do with the format of the email. The SMTP protocol uses ASCII. There are several ways you could send an email in a different character set, but all of them rely on some translation to ASCII in order for it to be sent with SMTP. Encoding the text (and/or attachments) using base64 is the simplest way of doing that.Is there a configuration process to maintain the English format from one to the other?
textI think it is not problem with FreeBSD and Windows 10 but specific email clients. Try different email client for FBSD. What is attached - file, text?
Unicode, UTF-8, ASCII?text