This morning I saw log entries I’ve never noticed before. They seem to have started 9 hours ago. First, this email arrived.
cliff2 is one one two hosts behind cliff:
[7:25 pro05 dvl ~] % host cliff cliff.int.unixathome.org has address 10.55.0.44 cliff.int.unixathome.org has address 10.55.0.14
In this post:
- FreeBSD 15.0
- Jan 18 18:34:48 cliff2 pkg[70008]: postfix upgraded: 3.10.3,1 -> 3.10.6,1
Of the 16 emails received, they were all about cliff2, never cliff1.
Date: Wed, 18 Feb 2026 12:22:30 +0000 (UTC) From: Mail Delivery System <MAILER-DAEMON@cliff2.int.unixathome.org> To: Postmaster <postmaster@cliff2.int.unixathome.org> Subject: Postfix SMTP server: errors from webserver.int.unixathome.org[10.55.0.3] Message-Id: <20260218122230.767072C399@cliff2.int.unixathome.org> Transcript of session follows. Out: 220 cliff2.int.unixathome.org ESMTP Postfix In: EHLO webserver.int.unixathome.org Out: 250-cliff2.int.unixathome.org Out: 250-PIPELINING Out: 250-SIZE 10485760000 Out: 250-ETRN Out: 250-STARTTLS Out: 250-ENHANCEDSTATUSCODES Out: 250-8BITMIME Out: 250-DSN Out: 250-SMTPUTF8 Out: 250 CHUNKING In: STARTTLS Out: 220 2.0.0 Ready to start TLS In: EHLO webserver.int.unixathome.org Out: 250-cliff2.int.unixathome.org Out: 250-PIPELINING Out: 250-SIZE 10485760000 Out: 250-ETRN Out: 250-ENHANCEDSTATUSCODES Out: 250-8BITMIME Out: 250-DSN Out: 250-SMTPUTF8 Out: 250 CHUNKING In: MAIL FROM:<nagios@webserver.int.unixathome.org> Out: 452 4.3.1 Insufficient system storage Session aborted, reason: lost connection For other details, see the local mail logfile
There were also a few email from MAIL FROM:
Log entries
The log entries for the sending host are:
Feb 18 12:22:30 webserver dma[15199]: new mail from user=nagios uid=181 envelope_from=<nagios@webserver.int.unixathome.org> Feb 18 12:22:30 webserver dma[15199]: mail to=<dan@langille.org> queued as 15199.3f8617a420a0 Feb 18 12:22:30 webserver dma[15199.3f8617a420a0][98813]: <dan@langille.org> trying delivery Feb 18 12:22:30 webserver dma[15199.3f8617a420a0][98813]: using smarthost (cliff.int.unixathome.org:25) Feb 18 12:22:30 webserver dma[15199.3f8617a420a0][98813]: trying remote delivery to cliff.int.unixathome.org [10.55.0.44] pref 0 Feb 18 12:22:30 webserver dma[15199.3f8617a420a0][98813]: remote delivery deferred: cliff.int.unixathome.org [10.55.0.44] failed after MAIL FROM: 452 4.3.1 Insufficient system storage Feb 18 12:22:30 webserver dma[15199.3f8617a420a0][98813]: trying remote delivery to cliff.int.unixathome.org [10.55.0.14] pref 0 Feb 18 12:22:30 webserver dma[15199.3f8617a420a0][98813]: <dan@langille.org> delivery successful
On the receiving host (cliff2), I found:
Feb 18 12:22:02 cliff2 postfix/smtpd[95569]: disconnect from webserver.int.unixathome.org[10.55.0.3] helo=1 quit=1 commands=2 Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: connect from webserver.int.unixathome.org[10.55.0.3] Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: Anonymous TLS connection established from webserver.int.unixathome.org[10.55.0.3]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: NOQUEUE: reject: MAIL from webserver.int.unixathome.org[10.55.0.3]: 452 4.3.1 Insufficient system storage; proto=ESMTP helo=<webserver.int.unixathome.org> Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: warning: not enough free space in mail queue: 15472168960 bytes < 1.5*message size limit Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: NOQUEUE: lost connection after MAIL from webserver.int.unixathome.org[10.55.0.3] Feb 18 12:22:30 cliff2 postfix/cleanup[98873]: 767072C399: message-id=<20260218122230.767072C399@cliff2.int.unixathome.org> Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: disconnect from webserver.int.unixathome.org[10.55.0.3] ehlo=2 starttls=1 mail=0/1 commands=3/4 Feb 18 12:22:30 cliff2 postfix/qmgr[7445]: 767072C399: from=<double-bounce@cliff2.int.unixathome.org>, size=1277, nrcpt=1 (queue active) Feb 18 12:22:30 cliff2 postfix/cleanup[98873]: 79B732C911: message-id=<20260218122230.767072C399@cliff2.int.unixathome.org> Feb 18 12:22:30 cliff2 postfix/local[98877]: 767072C399: to=<postmaster@cliff2.int.unixathome.org>, orig_to=<postmaster>, relay=local, delay=0.02, delays=0.01/0.01/0/0, dsn=2.0.0, status=sent (forwarded as 79B732C911) Feb 18 12:22:30 cliff2 postfix/qmgr[7445]: 79B732C911: from=<double-bounce@cliff2.int.unixathome.org>, size=1434, nrcpt=1 (queue active) Feb 18 12:22:30 cliff2 postfix/qmgr[7445]: 767072C399: removed Feb 18 12:22:30 cliff2 postfix/smtp[98880]: Untrusted TLS connection established to smtp.fastmail.com[103.168.172.60]:587: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 Feb 18 12:22:30 cliff2 postfix/smtp[98880]: 79B732C911: to=<dan@langille.org>, orig_to=<postmaster>, relay=smtp.fastmail.com[103.168.172.60]:587, delay=0.36, delays=0/0.01/0.11/0.23, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as CF51A800C2 ti_phl-compute-08_3001043_1771417350_11 via phl-compute-08) Feb 18 12:22:30 cliff2 postfix/qmgr[7445]: 79B732C911: removed
The mail queues on both hosts are empty.
Is it really a space issue?
No, it’s a mail configuration issue. See line 5, highlighted above.
That message repeats:
[12:35 cliff2 dvl ~] % sudo grep 'warning: not enough free space in mail queue' /var/log/maillog Feb 18 04:46:54 cliff2 postfix/smtpd[11796]: warning: not enough free space in mail queue: 15723220992 bytes < 1.5*message size limit Feb 18 04:47:35 cliff2 postfix/smtpd[11796]: warning: not enough free space in mail queue: 15720923136 bytes < 1.5*message size limit Feb 18 05:47:10 cliff2 postfix/smtpd[84061]: warning: not enough free space in mail queue: 15652507648 bytes < 1.5*message size limit Feb 18 06:31:40 cliff2 postfix/smtpd[3824]: warning: not enough free space in mail queue: 15704023040 bytes < 1.5*message size limit Feb 18 06:31:50 cliff2 postfix/smtpd[3824]: warning: not enough free space in mail queue: 15688192000 bytes < 1.5*message size limit Feb 18 06:32:20 cliff2 postfix/smtpd[3824]: warning: not enough free space in mail queue: 15684222976 bytes < 1.5*message size limit Feb 18 07:35:50 cliff2 postfix/smtpd[90728]: warning: not enough free space in mail queue: 15561146368 bytes < 1.5*message size limit Feb 18 07:40:51 cliff2 postfix/smtpd[10376]: warning: not enough free space in mail queue: 15549181952 bytes < 1.5*message size limit Feb 18 08:27:51 cliff2 postfix/smtpd[32105]: warning: not enough free space in mail queue: 15599861760 bytes < 1.5*message size limit Feb 18 08:27:51 cliff2 postfix/smtpd[38446]: warning: not enough free space in mail queue: 15599861760 bytes < 1.5*message size limit Feb 18 08:31:10 cliff2 postfix/smtpd[49465]: warning: not enough free space in mail queue: 15538733056 bytes < 1.5*message size limit Feb 18 08:31:41 cliff2 postfix/smtpd[49465]: warning: not enough free space in mail queue: 15529779200 bytes < 1.5*message size limit Feb 18 10:22:30 cliff2 postfix/smtpd[2402]: warning: not enough free space in mail queue: 15584747520 bytes < 1.5*message size limit Feb 18 11:22:30 cliff2 postfix/smtpd[6039]: warning: not enough free space in mail queue: 15494496256 bytes < 1.5*message size limit Feb 18 12:02:02 cliff2 postfix/smtpd[6761]: warning: not enough free space in mail queue: 15571550208 bytes < 1.5*message size limit Feb 18 12:22:30 cliff2 postfix/smtpd[95569]: warning: not enough free space in mail queue: 15472168960 bytes < 1.5*message size limit [12:35 cliff2 dvl ~] %
It seems someone wants to send a bigger message. 15GB email? I don’t think so. You’re not sending that. At first, I thought, I’ll just boost the limit. In this case, no. Don’t send me that email.
I suspect the email is from Nagios. I suspect the email is generated by a notification and for some reason, it has exploded.
Nagios restart
I’ve discovered that Nagios restart reproduces the problem.
Let’s deliver that email locally by commenting out this line from /etc/mail/aliases:
#root: dan@langille.org
… and restarting Nagios did not generate the issue.
What is also interesting, I’m seeing similar reports such as Postfix SMTP server: errors from unifi01.int.unixathome.org[10.55.0.131] – yet the mail log on unifi01 is empty. Logging is working:
[16:38 unifi01 dvl ~] % sudo cat /var/log/maillog Feb 18 00:00:00 unifi01 newsyslog[98880]: logfile turned over Feb 18 16:38:45 unifi01 dma[4d136][84888]: new mail from user=dvl uid=1002 envelope_from=<dvl@unifi01.int.unixathome.org> Feb 18 16:38:45 unifi01 dma[4d136][84888]: mail to=<dan@langille.org> queued as 4d136.372c11442000 Feb 18 16:38:45 unifi01 dma[4d136.372c11442000][84890]: <dan@langille.org> trying delivery Feb 18 16:38:45 unifi01 dma[4d136.372c11442000][84890]: using smarthost (cliff.int.unixathome.org:25) Feb 18 16:38:45 unifi01 dma[4d136.372c11442000][84890]: trying remote delivery to cliff.int.unixathome.org [10.55.0.14] pref 0 Feb 18 16:38:45 unifi01 dma[4d136.372c11442000][84890]: <dan@langille.org> delivery successful
Yet, cliff2 says mail came from there:
Feb 18 16:23:41 cliff2 postfix/smtpd[28059]: connect from unifi01.int.unixathome.org[10.55.0.131] Feb 18 16:23:41 cliff2 postfix/smtpd[28059]: Anonymous TLS connection established from unifi01.int.unixathome.org[10.55.0.131]: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (25 6/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 Feb 18 16:23:41 cliff2 postfix/smtpd[28059]: NOQUEUE: reject: MAIL from unifi01.int.unixathome.org[10.55.0.131]: 452 4.3.1 Insufficient system storage; proto=ESMTP helo=<unif i01.int.unixathome.org> Feb 18 16:23:41 cliff2 postfix/smtpd[28059]: warning: not enough free space in mail queue: 15225958400 bytes < 1.5*message size limit Feb 18 16:23:41 cliff2 postfix/cleanup[28068]: EF82B2C5A0: message-id=<20260218162341.EF82B2C5A0@cliff2.int.unixathome.org> Feb 18 16:23:41 cliff2 postfix/smtpd[28059]: disconnect from unifi01.int.unixathome.org[10.55.0.131] ehlo=2 starttls=1 mail=0/1 rset=1 quit=1 commands=5/6 Feb 18 16:23:41 cliff2 postfix/qmgr[7445]: EF82B2C5A0: from=<double-bounce@cliff2.int.unixathome.org>, size=1278, nrcpt=1 (queue active) Feb 18 16:23:41 cliff2 postfix/cleanup[28068]: F2A122BB68: message-id=<20260218162341.EF82B2C5A0@cliff2.int.unixathome.org> Feb 18 16:23:41 cliff2 postfix/local[28069]: EF82B2C5A0: to=<postmaster@cliff2.int.unixathome.org>, orig_to=<postmaster>, relay=local, delay=0.02, delays=0.01/0.01/0/0, dsn=2.0.0, status=sent (forwarded as F2A122BB68) Feb 18 16:23:41 cliff2 postfix/qmgr[7445]: F2A122BB68: from=<double-bounce@cliff2.int.unixathome.org>, size=1435, nrcpt=1 (queue active) Feb 18 16:23:41 cliff2 postfix/qmgr[7445]: EF82B2C5A0: removed Feb 18 16:23:42 cliff2 postfix/smtp[28070]: Untrusted TLS connection established to smtp.fastmail.com[103.168.172.60]:587: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 Feb 18 16:23:42 cliff2 postfix/smtp[28070]: F2A122BB68: to=<dan@langille.org>, orig_to=<postmaster>, relay=smtp.fastmail.com[103.168.172.60]:587, delay=0.65, delays=0/0.01/0.21/0.42, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 8FF3E80104 ti_phl-compute-08_3096974_1771431822_1 via phl-compute-08) Feb 18 16:23:42 cliff2 postfix/qmgr[7445]: F2A122BB68: removed
Now I’m wonderng if this is a Postfix configuration issue?
I did a postconf -n difference between the two hosts:
[12:00 pro05 dvl ~/tmp] % diff -ruN cliff1 cliff2 --- cliff1 2026-02-18 12:00:00 +++ cliff2 2026-02-18 11:59:20 @@ -1,4 +1,4 @@ -[16:59 cliff1 dvl ~] % postconf -n +[16:58 cliff2 dvl ~] % postconf -n alias_maps = hash:/etc/mail/aliases command_directory = /usr/local/sbin compatibility_level = 3.6 @@ -17,7 +17,7 @@ message_size_limit = 10485760000 meta_directory = /usr/local/libexec/postfix mydestination = $myhostname, localhost.$mydomain, localhost -myhostname = cliff1.int.unixathome.org +myhostname = cliff2.int.unixathome.org mynetworks_style = class newaliases_path = /usr/local/bin/newaliases queue_directory = /var/spool/postfix [12:00 pro05 dvl ~/tmp] %
Nothing.
Another source
Feb 18 18:02:02 dns-hidden-master dma[3ad8b][35058]: new mail from user=logcheck uid=915 envelope_from=<logcheck@dns-hidden-master.int.unixathome.org> Feb 18 18:02:02 dns-hidden-master dma[3ad8b][35058]: mail to=<dan@langille.org> queued as 3ad8b.51b887042000 Feb 18 18:02:02 dns-hidden-master dma[3ad8b.51b887042000][35110]: <dan@langille.org> trying delivery Feb 18 18:02:02 dns-hidden-master dma[3ad8b.51b887042000][35110]: using smarthost (cliff.int.unixathome.org:25) Feb 18 18:02:02 dns-hidden-master dma[3ad8b.51b887042000][35110]: trying remote delivery to cliff.int.unixathome.org [10.55.0.44] pref 0 Feb 18 18:02:02 dns-hidden-master dma[3ad8b.51b887042000][35110]: remote delivery deferred: cliff.int.unixathome.org [10.55.0.44] failed after MAIL FROM: 452 4.3.1 Insufficient system storage Feb 18 18:02:02 dns-hidden-master dma[3ad8b.51b887042000][35110]: trying remote delivery to cliff.int.unixathome.org [10.55.0.14] pref 0
Then I tried manually from that same source:
[18:03 dns-hidden-master dvl ~] % echo testing | mail dan@langille.org
The log entries:
Feb 18 18:03:51 dns-hidden-master dma[39652]: new mail from user=dvl uid=1002 envelope_from=<dvl@dns-hidden-master.int.unixathome.org> Feb 18 18:03:51 dns-hidden-master dma[39652]: mail to=<dan@langille.org> queued as 39652.3ee88ac42000 Feb 18 18:03:51 dns-hidden-master dma[39652.3ee88ac42000][45462]: <dan@langille.org> trying delivery Feb 18 18:03:51 dns-hidden-master dma[39652.3ee88ac42000][45462]: using smarthost (cliff.int.unixathome.org:25) Feb 18 18:03:51 dns-hidden-master dma[39652.3ee88ac42000][45462]: trying remote delivery to cliff.int.unixathome.org [10.55.0.44] pref 0 Feb 18 18:03:51 dns-hidden-master dma[39652.3ee88ac42000][45462]: remote delivery deferred: cliff.int.unixathome.org [10.55.0.44] failed after MAIL FROM: 452 4.3.1 Insufficient system storage Feb 18 18:03:51 dns-hidden-master dma[39652.3ee88ac42000][45462]: trying remote delivery to cliff.int.unixathome.org [10.55.0.14] pref 0 Feb 18 18:03:51 dns-hidden-master dma[39652.3ee88ac42000][45462]: <dan@langille.org> delivery successful
So, a very small message is triggering the event. I tried again. It is repeatable.
Simple telnet
telnet is a time honored tool. The following highlighted lines are the ones I typed.
[18:24 mydev dvl ~] % telnet cliff2 25 Trying 10.55.0.44... Connected to cliff2.int.unixathome.org. Escape character is '^]'. 220 cliff2.int.unixathome.org ESMTP Postfix EHLO mydev 250-cliff2.int.unixathome.org 250-PIPELINING 250-SIZE 10485760000 250-ETRN 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250-SMTPUTF8 250 CHUNKING MAIL FROM:dan@langille.org 452 4.3.1 Insufficient system storage
So, that’s the same as the stuff at the top of this post, apart from STARTTLS which I was not prepared to from within telnet.
I tried this with cliff1 – flawless. All good there.
Restarting postfix, then the jail
I’m sure it’s not space:
[16:54 r730-01 dvl ~] % zpool list NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT data01 5.81T 6.36G 5.81T - - 2% 0% 1.00x ONLINE - data02 928G 705G 223G - - 67% 75% 1.00x ONLINE - data03 7.25T 1.30T 5.95T - - 49% 17% 1.00x ONLINE - data04 29.1T 6.11T 23.0T - - 0% 21% 1.00x ONLINE - zroot 107G 47.9G 59.1G - - 54% 44% 1.00x ONLINE - [18:30 r730-01 dvl ~] % zfs list | grep cliff2 data02/jails/cliff2 4.00G 13.6G 2.46G /jails/cliff2
It’s all just one filesystem in there:
[18:36 cliff2 dvl ~] % zfs list no datasets available [18:36 cliff2 dvl ~] % df -h Filesystem Size Used Avail Capacity Mounted on data02/jails/cliff2 16G 2.5G 14G 15% /
Let’s try:
[18:30 cliff2 dvl ~] % sudo service postfix restart postfix/postfix-script: stopping the Postfix mail system postfix/postfix-script: starting the Postfix mail system [18:30 cliff2 dvl ~] %
That didn’t help.
I tried a jail restart, did not help:
[18:31 r730-01 dvl ~] % sudo service jail restart cliff2 Stopping jails: cliff2. Starting jails: cliff2.
Let’s try snapshots:
[18:37 r730-01 dvl ~] % zfs list -r -t snapshot data02/jails/cliff2 | grep -v @autosnap NAME USED AVAIL REFER MOUNTPOINT data02/jails/cliff2@mkjail-202509051453 725M - 2.24G - data02/jails/cliff2@mkjail-202602101242 716M - 2.38G -
Let’s destroy those two:
[18:37 r730-01 dvl ~] % sudo zfs destroy data02/jails/cliff2@mkjail-202509051453 [18:37 r730-01 dvl ~] % sudo zfs destroy data02/jails/cliff2@mkjail-202602101242
Umm, that seems to have fixed it:
[18:39 mydev dvl ~] % telnet cliff2 25 Trying 10.55.0.44... Connected to cliff2.int.unixathome.org. Escape character is '^]'. 220 cliff2.int.unixathome.org ESMTP Postfix EHLO mydev 250-cliff2.int.unixathome.org 250-PIPELINING 250-SIZE 10485760000 250-ETRN 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250-SMTPUTF8 250 CHUNKING MAIL FROM:dan@langille.org 250 2.1.0 Ok
WTF?
[18:39 r730-01 dvl ~] % zfs list data02/jails/cliff2 NAME USED AVAIL REFER MOUNTPOINT data02/jails/cliff2 2.53G 15.0G 2.46G /jails/cliff2 [18:39 r730-01 dvl ~] % zpool list data02 NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT data02 928G 704G 224G - - 66% 75% 1.00x ONLINE - [18:40 r730-01 dvl ~] %
No quota or reservation
The pool had 223G free at the start of this.
Let’s look around…
[18:40 r730-01 dvl ~] % zfs get all data02/jails/cliff2 | grep quota data02/jails/cliff2 quota none default data02/jails/cliff2 refquota none default data02/jails/cliff2 defaultuserquota 0 - data02/jails/cliff2 defaultgroupquota 0 - data02/jails/cliff2 defaultprojectquota 0 - data02/jails/cliff2 defaultuserobjquota 0 - data02/jails/cliff2 defaultgroupobjquota 0 - data02/jails/cliff2 defaultprojectobjquota 0 - [18:41 r730-01 dvl ~] % zfs get all data02/jails | grep quota data02/jails quota none default data02/jails refquota none default data02/jails defaultuserquota 0 - data02/jails defaultgroupquota 0 - data02/jails defaultprojectquota 0 - data02/jails defaultuserobjquota 0 - data02/jails defaultgroupobjquota 0 - data02/jails defaultprojectobjquota 0 - [18:41 r730-01 dvl ~] % zfs get all data02 | grep quota data02 quota none default data02 refquota none default data02 defaultuserquota 0 - data02 defaultgroupquota 0 - data02 defaultprojectquota 0 - data02 defaultuserobjquota 0 - data02 defaultgroupobjquota 0 - data02 defaultprojectobjquota 0 - [18:41 r730-01 dvl ~] % zfs get all data02 | grep reserve [18:41 r730-01 dvl ~] % zfs get all data02 | grep res data02 compressratio 1.79x - data02 reservation none default data02 compression zstd received data02 aclinherit restricted default data02 sharesmb off default data02 refreservation none default data02 usedbyrefreservation 0B - data02 refcompressratio 1.00x - [18:41 r730-01 dvl ~] % zfs get all data02/jails/cliff2 | grep reservation data02/jails/cliff2 reservation none default data02/jails/cliff2 refreservation none default data02/jails/cliff2 usedbyrefreservation 0B - [18:42 r730-01 dvl ~] % zfs get all data02/jails | grep reservation data02/jails reservation none default data02/jails refreservation none default data02/jails usedbyrefreservation 0B - [18:42 r730-01 dvl ~] % zfs get all data02 | grep reservation data02 reservation none default data02 refreservation none default data02 usedbyrefreservation 0B - [18:42 r730-01 dvl ~] %
So, what was blocking this?
