Strange Link Additional Code

I made an email with a button. The link is

When I’m pressing the button in the email the link has changed as follows:

Where does this oh so long string come from?

It is a mjml template.

Your software
My Mautic version is: 5.0.4
My PHP version is: 8.1.27
My Database type and version is:

Hello, seems, that this is added by your smtp provider.
Which one do you use? Maybe Sendgrid?
Also: is click tracking turned on your your SMTP provide’s panel?

Hello Joey

I’m using Postfix on my own mail server.

What’s the advantage of sending via a SMTP provider?
Is it that my server does not land on a black list as SPAM mail server, when sending several thousand emails per day?

Append tracking pixel into email body ? Is 'On" which should be okay, in order to track opening of mail.

I just checked another old campaign, which worked perfectly with Mautic 4. And now there is also added this strange code.