Please note: Automatic replies, such as out-of-office notifications will be sent to the From address, not the Reply-To. Reply-To is only used when the person who received the email clicks the Reply button in their email client.
Note :- The SMTP envelope sender typically appears as <uniqueidentifier>@*.mktomail.com. You will only receive responses of this nature if you have configured a branded sender for your subscription. While this serves as the correct destination for auto-responses, regrettably, it is frequently overlooked.