How can I enable quotas or size limits on users mailboxes?
This is not really a function of Postfix, although if you are using mbox-style mailboxes, you may achieve what you’re looking for with the mailbox_size_limit parameter. Be aware that if you use maildir style mailboxes this parameter only limits the size of individual mail files and not the size of the entire mailbox. Mailbox quotas are best enforced by the mail store itself, which might be done through normal operating system accounting or your IMAP server configuration. Be aware that if your IMAP server receives messages over LMTP, over-quota situations won’t be discovered until after Postfix has accepted the message, so it will have to be bounced. If you want to reject mail for users over their quotas, you’ll have to use an access table listing users who are over their quotas.
