TL;DR: You can’t remove those links because they are required by Email Service Providers (ESPs) when we deliver mail on your behalf.
The modern world is full of technology that allows us to connect instantaneously with anyone on the planet. You can pick up the phone in your pocket and know virtually any piece of information that you would like.
Unfortunately for us, email, that old workhorse of business life, was designed decades ago, before many of us were even born. When you press send on that message it travels between ESPs, being checked at every stage for possible spam or malicious content.
The purpose of SendWP is to make sure that your emails are delivered as you expect. This is a complicated process of establishing a trust relationship between our service and other ESPs so that every email we send gets through their content filters. A big part of building trust is providing transparency to their users (the recipient of the email) about who has touched the email that was delivered.