Postmark requires a minimum of 50K emails a month for a dedicated IP address, and they state that minimum is for quality reasons. You won't get a good enough r

Postmark requires a minimum of 50K emails a month for a dedicated IP address, and they state that minimum is for quality reasons. You won't get a good enough reputation on your IP without it. That should give people an estimate of the required volume to get decent delivirability rates to big providers.