Email HTML injection with a simple tip

What is the Bug?

one of these domains at the end of the web page there is an option to subscribe to get emails about the company.

I filled it with a random data like this

I sent it to test the behavior of this form; after sending I received a confirmation email like this

I observed that the name is reflected in the email and rendered in HTML.

The first payload comes to my mind is

But if I tried to send it the form doesn’t accept it and the response is 403 but there is no a WAF to block my payloads, with some time I realized this a problem of payload size.
The name input field allows a maximum of 35 characters.

So I sent this payload

this is the result

I reported it and this is the triage reply

Now I have a challenge to make the payload short and more obvious

After some search I found there is a way to make any link in short form
like subdomain.verylong.com -> bit.ly/some_random_chars

you can discover this here https://app.bitly.com/
I signed up in this site and made a short link for https://google.com

and make my final payload

which results this

and this also