Gmail's multiple account support distinguishes between Gmail accounts with just an index, which simply reflects the order in which you signed into Gmail:
So if you sign into Gmail first with
firstname.lastname@example.org and then with
email@example.com, https://mail.google.com/mail/u/0/ will go to the inbox of
firstname.lastname@example.org; but if you sign into
email@example.com, the same link will go to the inbox of
Aside from always signing into Google accounts in the same order, is there a good way to link to a specific Gmail account?
See also this related question on Google Groups.