@pitaj Hmm... Does Debian still ship with Exim by default? Does Exim rename their executable to sendmail? I'd thought not but been a while since I used it. I think OP is using Ubuntu (wh/includes Postfix's sendmail executable as shipped). But they maybe on Deb? Just to clarify.
Edit: Yeah, Debian does still include Exim by default https://wiki.debian.org/Exim