We have started purging defunct accounts: users whose email addresses don’t seem to be valid anymore.
We are not doing this in a hurry, but instead are trying to be methodological about it: if someone’s email bounces, and we see they haven’t logged in during the past 6 months, we are going to assume this user doesn’t exist within that organization anymore, i.e. has probably left the company where they were previously working.
(The 6 months of no-activity helps us avoid temporary email problems, such as when someone’s email server is down for a day.)
Also getting purged are new users with invalid emails: this can happen when an existing user mistypes a coworker’s email address at the time they invite people to join their teams.
An account is created at the time someone initiates the invitation, but if we find the email associated with that account is bouncing, we will delete that account.