A mail address to which to reply (optional).
def get_reply_to() -> str: ... def set_reply_to(value: str) -> None: ...
reply_to = property(get_reply_to, set_reply_to)
If this property contains a non-empty string, a Reply-To SMTP header is created for the message. This header shows the address to use for replies (useful if this address is different from the one in from_).
If the resulting header is longer than MaxHeaderLength, then it is folded according to RFC 822 specifications.