Hi,
How can I automatically set mail rate limiting, depending on plan?
Say, “Basic” plan limits 10 messages a day, “Advanced” - 100, etc. Trying to control the potential spam.
Please advice. I would really appreciate. I can try to return the favor 
Solved it on my own. Not the best solution, but does the job.
/etc/mail/greylist.conf
Limits 50 messages per 12 hours per user
ratelimit “virtualmin_limit” rcpt 50 / 720m key “%f”
racl greylist from /.*/ ratelimit “virtualmin_limit” delay 721m autowhite 0m msg “Message quota exceeded”
racl whitelist default