I spent last week setting up email servers with trying all MTA and I was able to send and receive emails with attachments and do spam filtering.
Now my concern is what if I got too many users and too many domains with emails that have attachments. By time servers' quota would be used and there will be no space.
My question is, how to setup dynamic servers to serve emails? I want it to be flexible like I will add multiple domains and users and I can't give each domain it's own server because they may add later more users. Simply, I want to setup a service that scale.
To be clearer, I want to make a service like Google Apps and Zoho Mail.