The issue was a new version of docker and as a result of that the system was indeed actually running out of space. I thought the system had plenty of space, but it actually didn’t.
I have docker use a separate mount for /var/lib/docker so it doesn’t put non-essential stuff in my VM backup (PVE -> (almost pristine) Ubuntu -> docker -> postfix in a container). All data lives outside theVM. As this part of my 2-server setup kept receiving messages (mail kept working and it was the active server and /var/lib/docker had enough space) I thought the out of storage message was weird. But it wasn’t and I overlooked actual storage on / (yes, that is 'stupid me') I recently had to rebuild my setup when an internal hard disk completely died (good test, I was able to recover fully within a reasonable amount of time) and the new docker containerd uses /var/lib/containerd for storage (used to be /var/lib/docker). This lived on the (small) / volume (16GB) and it quickly had filled up with images. Thanks for your help Viktor, it actually made me look and see what was really going on. And now I will have to wait until 4xx deferred messages are delivered after all. Because I did not see your reply until I checked https://www.mail-archive.com/[email protected]/msg107892.html G > On 11 May 2026, at 10:29, Gerben Wierda <[email protected]> wrote: > > I get two of these from double-bounce@ <mymailserver> > > Return-Path: <double-bounce@<mymailserver>> > Delivered-To: gerben@<mymailserver> > Received: from <mymailserver> > by snape.rna.nl with LMTP > id /fHmMkhEAWrVGAAAy+4yzw > (envelope-from <double-bounce@<mymailserver>>) > for <gerben@<mymailserver>>; Mon, 11 May 2026 02:51:52 +0000 > Received: by <mymailserver> (Postfix) > id CCB1FA290A; Mon, 11 May 2026 02:51:52 +0000 (UTC) > Date: Mon, 11 May 2026 02:51:52 +0000 (UTC) > From: Mail Delivery System <MAILER-DAEMON@<mymailserver>> > To: Postmaster <postmaster@<mymailserver>> > Subject: Postfix SMTP server: errors from unknown[101.47.29.67] > Message-Id: <[email protected]> > > Transcript of session follows. > > Out: 220 mail.rna.nl > In: EHLO cangrang.cn > Out: 250-snape.rna.nl > Out: 250-PIPELINING > Out: 250-SIZE 25165824 > Out: 250-ETRN > Out: 250-STARTTLS > Out: 250-ENHANCEDSTATUSCODES > Out: 250-8BITMIME > Out: 250-DSN > Out: 250 SMTPUTF8 > In: STARTTLS > Out: 220 2.0.0 Ready to start TLS > In: EHLO cangrang.cn > Out: 250-snape.rna.nl > Out: 250-PIPELINING > Out: 250-SIZE 25165824 > Out: 250-ETRN > Out: 250-AUTH CRAM-MD5 > Out: 250-ENHANCEDSTATUSCODES > Out: 250-8BITMIME > Out: 250-DSN > Out: 250 SMTPUTF8 > In: MAIL FROM:<[email protected]> > Out: 452 4.3.1 Insufficient system storage > In: QUIT > Out: 221 2.0.0 Bye > > Now, I get two of these 2 minutes apart for two different IP-addresses (one > China, one Hong Kong, and this is weird too because my router should block > incoming from China, that is handled by another MX) Anyway, looking in the > log, I see an active spammer being rejected: > > May 11 06:59:53 mymailserver smtp_haproxy/postscreen[6992]: CONNECT from > [101.47.29.196]:50413 to [192.168.2.2]:25 > May 11 06:59:53 mymailserver postfix/dnsblog[6993]: addr 101.47.29.196 listed > by domain zen.spamhaus.org as 127.0.0.11 > May 11 06:59:53 mymailserver postfix/dnsblog[6993]: addr 101.47.29.196 listed > by domain zen.spamhaus.org as 127.0.0.3 > May 11 06:59:53 mymailserver smtp_haproxy/postscreen[6992]: DNSBL rank 1 for > [101.47.29.196]:50413 > May 11 06:59:58 mymailserver smtp/smtpd[6987]: connect from > unknown[101.47.29.196] > May 11 06:59:59 mymailserver smtp/smtpd[6987]: NOQUEUE: reject: RCPT from > unknown[101.47.29.196]: 450 4.7.1 Client host rejected: cannot find your > reverse hostname, [101.47.29.196]; from=<[email protected]> > to=<[email protected]> proto=ESMTP helo=<qvwendi.cn> > May 11 06:59:59 mymailserver smtp/smtpd[6987]: disconnect from > unknown[101.47.29.196] ehlo=2 starttls=1 mail=1 rcpt=0/1 quit=1 commands=5/6 > > This is normal stuff in my log. At some point this bad operator was rate > limited. Good. But why do I get the messages from double-bounce@ in this > case? And why is my postfix sending out > 452 4.3.1 Insufficient system storage > if it's operating normally (receiving and sending mail and all)? > > Gerben Wierda (LinkedIn <https://www.linkedin.com/in/gerbenwierda>, Mastodon > <https://newsie.social/@gctwnl>, Bluesky > <https://bsky.app/profile/gerbenwierda.bsky.social>) > R&A IT Strategy <https://ea.rna.nl/> (main site) > Book: Chess and the Art of Enterprise Architecture > <https://ea.rna.nl/the-book/> > Book: Mastering ArchiMate <https://ea.rna.nl/mastering-archimate-edition-3-2/> > YouTube Channel <http://www.youtube.com/@GerbenWierda> Gerben Wierda (LinkedIn <https://www.linkedin.com/in/gerbenwierda>) R&A Enterprise Architecture <https://ea.rna.nl/> (main site) Book: Chess and the Art of Enterprise Architecture <https://ea.rna.nl/the-book/> Book: Mastering ArchiMate <https://ea.rna.nl/mastering-archimate-edition-3-2/>
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