How to sign in to CC with alternative email address to share files

A colleague's Adobe login is his school email address (he bought Adobe CS for his course). I need him to be able to access some of my files and assets stored in my libraries for collaboration on projects. I would prefer to use his company email address (rather than the school one) for sharing those assets to avoid a big re-do in a year or two time when he graduates college and loses that email address. He has set his work address up as a secondary address in Adobe, but cannot log in with it (it says incorrect password when he uses the same one as his primary address). Is there any way that we can have it so that he can use a work email address to share folders of files and libraries?

If I send a share link to his company email address, he does not see the folder, yet he sees anything I have shared with his college email address.

Our plan it to move all our company marketing assets to CC for easy editing and updating by two people, so I need to be sure that we can never 'lose' access to assets down the line if someone leaves or changes email address.

Can anyone offer any advice please?

Thanks in advance.