==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.3.2
- Deployed with iRedMail Easy or the downloadable installer? Downloadable
- Linux/BSD distribution name and version: CentOS Linux release 7.7.1908
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Today our iRedMail server started bouncing mail sent to some users with "552 5.5.2 Recipient address rejected: Mailbox is full" messages.

I have no quotas set at the System level, the domain level, or the user level. All users say "XX of Unlimited" near their listing, and inside their settings, no users have any value in the quota field.

When this first started happening, I took a look at the disk space on the server, and it was high utilization - 97% for the mail store, but still several GB left. No complaints in the logs of write errors because of no actual disk space left.

I found a couple users I could delete to recover some space, and set them to be deleted in 1 day, the minimum allowed by iRedAdmin-Pro, and then I went in via the command line and purged those directories' cur mailboxes to recover about 10GB. Currently, the mail store disk is at 91%, and I will be growing the disk later in the week.

However, recovering this space doesn't seem to have fixed the problem. Mail was still bouncing, and only to some accounts. I'm not sure what the threshold is, but some users were still receiving mail just fine, and some weren't, my account included.

As a test, I added a quota to my account, far above my current utilization, and that allowed mail to get through, so for a temporary fix, I've added quotas to the accounts which were bouncing.

The maillog for one of these bounces simply says the following:

Sep 20 16:22:09 mail postfix/smtpd[2465]: NOQUEUE: reject: RCPT from anon.anon.net[1.2.3.4]: 552 5.2.2 <my.user@mydomain.com>: Recipient address rejected: Mailbox is full; from=<sender@sender.com> to=<my.user@mydomain.com> proto=ESMTP helo=<anon.anon.net>

iRedAPD's log line for that mail doesn't look any different than emails which are getting to users which aren't having the problem, simply saying DUNNO for the return, which if I'm reading the config file correctly, is the pass condition for quotas if I had them enabled.

What should I be looking at?

My hope is to turn the quotas back off for these users, but I will be growing the disk to a point where I can set the quotas pretty high. I just don't want to have to manage for oversubscription.

Thanks for any help.