English language thank you letter help

[Prokupatuscrakedatus]

I need help with a thank you letter:
adressee: an American ex university prof in his 80ties
reason: doanted two items (important to him and gratefully received) to the archives of a small literary society.

My problem is the proper greeting and sign off.
DH has met him once.

Thanks for your help!

I’d say ‘Dear Professor

With very best wishes

Your name

Thank you,
I'll use you suggestion.
Greetings and sign offs are a linguistic and cultural nightmare. There are so many ways of getting it wrong.

Definitely dear professor but maybe sign off with 'kindest regards' if your DH doesn't know him that well?

kindest regards ....
Ok - better err on the side of formality, then.
And he his in his eighties after all.

If you want to err on the side of formality, the correct sign off in a letter for someone addressed by name would be "yours sincerely" (formal) or "yours truly" (for an acquaintance). "Kindest regards" is a more informal sign off for emails.

The professor bit is more tricky as to whether he is a professor emeritus and has retained his title or not. On the other hand, it would be rude to call him Mr if his correct title is Professor. No one would be offended by being called Professor if they are a Mr so best to stick to that.

Perhaps you could ask Jacob Rees-Mogg...

I knew it - a nightmare!!
We do not have to be that formal, and - I have just found out - it will be an e-mail ... so a middle ground should be OK plus he knows we aren't English speakers.

It is a lovely field of linguistics, though.