Recommended quota in Postfix/PolicyD?

Good morning!

I've got a linode configured as a mail server only. It's purpose is basically for outgoing emails (and to collect BOUNCES etc.). We're using SPF, DKIM signing, and now I've setup Cluebringer/PolicyD v2 to control the sending rate.

What is a recommended quota? With our previous hosting provider, we were limited to 300 emails per 30 minutes, which wasn't enough. It's probably 30 customers who will send emails through our new mail server. The biggest difference now from before is SPF and DKIM which wasn't in use before. Does that mean we will be able to increase the amount of emails sent over time?

I've tried to google this but very hard to find something good. Best would be if the policy paused and queued up all emails, as of now they are Deferred/Rejected which isn't good.

Anu suggestions? I'm trying to be as careful as I can in order to keep a good reputation but ti's hard when I don't know what's recommended.

Thanks!