From: Sven Westenberg on
Hallo,

we use postfix as a mail relay in our DMZ. There are no local users,
who receive mails. From time to time external senders receive the
reply code 552 Requested mail action aborted: exceeded storage
allocation from our postfix mta. All e-mails were just a few kB big
and the receiver mail-boxes were not full at all.

My question now is: In what scenarios does postfix answer with this
code (although there are no local users setup on the relay itself)?
Does postfix have constraints about the overall size of the queue?
What I mean ist the sum of all deferred e-mails, which can not be
delivered immediately. Is there a parameter, which prevents, that the
whole disk space is used up by deferred e-mails?

Thank you for your help.
Sven