If the "Sender notified by Mailtrack" signature ad is removed from an email before you send it then there will normally be no visible sign that the email is being tracked.
A "foot print" is left, so to speak, in the form of the snippet of code used for the tracking, however the recipient would have to actively check for this by viewing the source code of the sent message.
A "foot print" is left, so to speak, in the form of the snippet of code used for the tracking, however the recipient would have to actively check for this by viewing the source code of the sent message.