When sending an email to a contact that has an autoresponder / out-of-office message enabled on their email account, you may find that the autoresponder is being sent to the 'From' address, rather than the 'Reply-to' address.
This occurs because the 'Reply-to' email address is only used when an end-user clicks 'reply' on the received email; as per the standard (see 'Technical Information', below) - as such, most automated email responses will be sent to the 'From' email address. This behaviour is out of our control.
Technical standards require that automated email replies only go to the 'From' address. This is outlined in relevant standards documentation from the Internet Engineering Task Force (IETF); an internet standards body.
As this is an internet standard, this behaviour is out of our control.