I tried to send emails to five users on ruwiki. To do this, I opened their user pages in different tabs and hit "Email user" on each. Unfortunately, when I tried to send the first email, I immediately ran into an error message:

Action throttled
As an anti-abuse measure, you are limited from performing this action too many times in a short space of time, and you have exceeded this limit. Please try again in a few minutes.

even though I hadn't sent a single email. (I was told in #wikimedia-tech that this is not how it's supposed to work, hence this report.)