There is only one main rule - do NOT disturb others. We do not have any strict restrictions, but this should not be abused.
There are no restrictions on the number of accounts, sites, mailboxes, number of outgoing emails, traffic, etc. But everything is within reasonable limits and we reserve the right to determine what is reasonable at our discretion.
All is needed from you, is to realize that in addition to your sites, the server also serves many others. This means you should not single-handedly and for a long time occupy all the processor cores, occupy the entire internet channel, and so on. And of course, in no case should you setup everyone by engaging in any illegal activity. For example, sending spam, which can lead to IP address blocking at various many email services. You cannot engage in phishing, hacking, posting illegal (in the country where the server is physically located) content, etc., for which the server can be completely disconnected from the data center.