Rate limit
There is a rate limit for the public beta launch. *Rate limit on registrations per IP is currently 10 per 3 hours *Rate limit on certificates per Domain is currently 5 per 7 days
The plugins must track this to ensure a good functioning plugin. We have to track the requests per hour and limit the request. Maybe a queue will be handy to have in this situation.
Thanks to zEitEr from DirectAdmin forums for reporting this issue: http://forum.directadmin.com/showthread.php?t=51588&p=269400#post269400
I think that rate limit information is out of date. https://community.letsencrypt.org/t/rate-limits-for-lets-encrypt/6769 I don't think any of the limits are a problem for normal usage.