This is just based on trial-and-error testing, but when I submit over 70 e-mail addresses at:
https://www.yammer.com/[my domain]/admin/blocked_email_addresses
I get one of the following errors:
- Nginx 502 Bad Gateway
- We’re sorry, but something went wrong.
We’ve been notified about this issue and we’ll take a look at it shortly.
When I submit 70 addresses or fewer, it works as expected.
I have not yet discovered a way to block addresses via PowerShell.