email - How to wish someone "Happy New Year" in a professional, formal and friendly way

English is my second language. I still struggle with it especially when I have to write a formal email.

I need to send an email to several of my business associates in reply to theirs. It contains some technical explanation related to our project, after which I would like to wish them Happy New Year. What is a professional, formal and friendly way to say this?

Answer

How about

Dear X,

Regarding the explanation of our project bla bla...

And finally,
Wish you and your family a

very Happy New Year.

Looking forward to working with you next year.

Regards,

or

Dear X,

Wish you and your family a
very Happy New Year.

Regarding the project matter for discussion bla bla

Regards,

Either of these should be fine.
The reference to "family" or "loved ones" makes it less formal - but is still professional.