I hidden my email after this dialogue in Telegram. Before that, the email was public.
That envelope you see marked by suchmoon is displayed only in OUTBOX messages -> messages you have sent.
The alleged Alex_Sr telegram account approached you with a screenshot of your own OUTBOX msgs. Nobody except you has access to those unless you prove you've been hacked.
Technically it is possible for the "envelope" icon to be visible for other users if they made their e-mail address public. I have their profile scraped a week ago and that wasn't the case. So barring some precisely timed ninja-edits to coincide with when Alex_Sr allegedly took that screenshot, I think it's safe to say the telegram chat is fake.
Edit: removed my thoughts on telegram as it's not actually showing up as I expected.