Either of these addresses work for me:
dbayer@barnard.edu
bayer@math.columbia.edu
I use Sanebox to prioritize the many email messages that I receive each week. If you write me from an academic address such as Barnard or Columbia, then I will see your message right away. If you write me from an unfamiliar personal email address, then there is a risk that I won’t see your message.
Please use your Barnard or Columbia uni, not a “vanity” email address that Columbia might have offered you. You were not warned that our software is unable to handle email aliases. For one example, I cannot add you as an NRA Student to CourseWorks using the “People” tool, because I don’t know your uni, and I cannot add you using the “Guest User” tool, because it disallows Columbia email addresses. If you’re writing to ask for my help, begin by including your uni. Otherwise, it takes an extra round of email exchanges just to ask.