Late submission of supplemental Rec letters

I am applying to several Harvard and Columbia, but only submitted the two required teacher recs before the deadline. I was considering adding another recommendation from a research mentor. Is that possible past the Jan.1 deadline for the Common App?
Additionally, I applied to Columbia, and I had to add my research mentor’s email on the Common App. What do they do with that Email?

You can always add it. Worst case they will not look at it but they probably will. No one is in the office until at least tomorrow or later.

No idea what Columbia does but I think they will contact your research mentor since they ask for an email