How to address a professor in an office setting I will be working at a private company as an engineer (but in a heavily research oriented team), and I just learned the contact information of my manager. I will be sending an email to introduce myself, but I am not sure how to address him.

Just by searching his name online, I learnt that he works as a professor at a university (but is on a leave of absence, at least his page says so) but his current title in the company is engineer. So, in this case, should I address him as "Professor surname" or "Dr _surname" in the email or just by his first name (which is the preffered way at this company)?
If you're here in the US, I'd go with Dr. You're addressing him as your supervisor at a workplace, not at an academic institution.  He's not a professor there.  His title there is probably something like "Director of Research" which is definitely not how you'd address him. But he is a Dr. and, in my experience in 40+ years in industry, that is how he'd be addressed.

But also, at most universities here in the US, lots of instructors who do not have PhDs and are not on tenure track are still called professor.  Like me.  I don't have a PhD and my official title is lecturer, but students and others commonly address me as professor nonetheless.  (And yes, it makes me a little uneasy because, to me, there is a difference and calling anyone a professor regardless of whether they really are seems to cheapen the title for those who've actually earned it, which I have not.)