Need INFO

Can somebody from support explain mail quota for 24 hours for custom/own domain - are is per domain or per username? For example under mail policy I have Incoming and Outgoing mail limits - are they for all users mail/accounts - or they apply separated for every user - i.e. - Maximum email size/day (MB) - 300MB - is that for every account or it's 300 megs for summary accounts traffic in my domain? The same question for number of emails, recipients etc. limits?
Thank you in advance for answer