Depend on situation, for example you set mailbox rate limit to 10/minute, your client send 1 mail containing 20 recipients, if client send this in one bulk (all at one session) this mail is not send never because 20 > 10 all the time.
If client send those 20 mails one by one first minute is delivered 10 mails and 10 mails is rejected, now it’s your client (Outlook, Thunderbird,…) job to know those mails was rejected and those needs to be send once again in future. If it resend them after 1 minute period all remaining 10 can will be send, but once again it’s your client job.
This is basic example how Mailcow ratelimiting works. If you want different approach you can modify your extra.conf like this
# Soft rate limiting
smtp_destination_concurrency_limit = 2
smtp_destination_rate_delay = 13
smtp_extra_recipient_limit = 7
This is “softer” limitation on postfix, basiclly if you do not set MC rate limiting mechanism this will accept all messages from your clients to Postfix queue and send by those limits, but be aware as always wrong configuration can make long waiting queue, got pleasure to see queue for 2 days long to send mail, so some extra monitoring of your queue will be nice,…. And as always please visit docs