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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘postfix’ Category

Some scripts and tips for easing the maintenance of a postfix based SMTP system

Posted by jpluimers on 2021/11/24

A few scripts and tips I found Googling around.

Deleting queued messages by regular expression pattern

I have seen the below script numerous time, usually without any attribution (for instance [Wayback] Postfix Flush the Mail Queue – nixCraft and  [Wayback] – Following script deletes all mail from the mailq which matches the regular expression specified as the first argument · GitHub).

The earliest version I could find was in [Wayback] ‘Re: delete messages from mailq’ – MARC by [Wayback] ‘Ralf Hildebrandt ‘ posts – MARC:

--- snip ---

$REGEXP = shift || die "no email-adress given (regexp-style, e.g. bl.*\!";

@data = qx</usr/sbin/postqueue -p>;
for (@data) {
  if (/^(\w+)\*?\s/) {
     $queue_id = $1;
  if($queue_id) {
    if (/$REGEXP/i) {
      $Q{$queue_id} = 1;
      $queue_id = "";
#open(POSTSUPER,"|cat") || die "couldn't open postsuper" ;
open(POSTSUPER,"|postsuper -d -") || die "couldn't open postsuper" ;

foreach (keys %Q) {
  print POSTSUPER "$_\n";
--- snip ---

And then use:
% delete-from-mailq "^test"



[Wayback] How do I check the postfix queue size? – Server Fault

Lots of great answers and pointers to useful guides/software there.


[Wayback] Postfix Bottleneck Analysis points to [Wayback] Postfix manual – qshape(1): qshape - Print Postfix queue domain and age distribution, then explains about different scenarion and queues:


postqueue -p | tail -n 1

Last line in the postqueue -p shows how many requests and size:

-- 317788 Kbytes in 11860 Requests.

View queues size

I tried finding the original posting of the below script, but could not. If you find it, please let me know.

#!/usr/bin/env perl

# postfix queue/s size
# author: 
# source:

use strict;
use warnings;
use Symbol;
sub count {
        my ($dir) = @_;
        my $dh = gensym();
        my $c = 0;
        opendir($dh, $dir) or die "$0: opendir: $dir: $!\n";
        while (my $f = readdir($dh)) {
                if ($f =~ m{^[A-F0-9]{5,}$}) {
                } elsif ($f =~ m{^[A-F0-9]$}) {
                        $c += count("$dir/$f");
        closedir($dh) or die "closedir: $dir: $!\n";
        return $c;
my $qdir = `postconf -h queue_directory`;
chdir($qdir) or die "$0: chdir: $qdir: $!\n";
printf "Incoming: %d\n", count("incoming");
printf "Active: %d\n", count("active");
printf "Deferred: %d\n", count("deferred");
printf "Bounced: %d\n", count("bounce");
printf "Hold: %d\n", count("hold");
printf "Corrupt: %d\n", count("corrupt");

Various commands

[Wayback] Inspecting Postfix’s email queue – Tech-G explaining about:

  • mailq
  • postqueue -p
  • postcat -vq XXXXXXXXXX (where XXXXXXXXXX is the message ID)
  • postqueue -f / postfix flush
  • postsuper -d to delete messages

More of these in [Wayback] Postfix Mail Queue Management – Linux Hint and [Wayback] Postfix Bottleneck Analysis: queues.


Based on [Wayback] Using “make” for Postfix file maintenance

MAPS = relays.db aliases.db transport.db relocated.db \
        virtual.db sender_checks.db rejected_recips.db \

all : $(MAPS)

aliases.db : aliases

%.db : %
        postmap $*

This is my Makefile that runs fine on Tumbleweed (note: all 8-space indents are TAB characters):

MAPS =  /etc/aliases.db \
        transport.db \
        virtual.db \
        helo_access.db \
        canonical.db \
        sasl_passwd.db \
        relocated.db \
        relay.db \
        access.db \
        relay_ccerts.db \

all : $(MAPS)

aliases.db : aliases
        @echo "Rebuilding $@."

%.db : %
        @echo "Rebuilding $@."
        postmap $*

In the future, I might try [Wayback] Makefile.postfix · GitHub, though I think it is convoluted:

## Postfix: Makefile to update *.db files
POSTCONF= /usr/sbin/postconf
POSTMAP= /usr/sbin/postmap
default: postmap
postmap: Makefile.postmap
@echo 'Updating database files …'
$(MAKE) -f Makefile.postmap
@echo 'Updating $@ …'
@set -e; \
rm -f $@.$$$$.tmp; \
echo 'POSTMAP=$(POSTMAP)' >>$@.$$$$.tmp; \
echo 'postmap::' >>$@.$$$$.tmp; \
config_directory="$(PWD)"; \
{ $(POSTCONF) -c $(PWD) || kill $$$$; } \
|tr ' ' '\n' \
|sed -n \
-e 's/,$$//' \
-e 's#^hash:\$$config_directory/##p' \
-e 's#^hash:'"$$config_directory/##p" \
|sort -u \
|while read mapfile; do \
echo "postmap:: $$mapfile.db" >>$@.$$$$.tmp; \
echo "$$mapfile.db: $$mapfile" >>$@.$$$$.tmp; \
echo " \$$(POSTMAP) $$<" >>$@.$$$$.tmp; \
done; \
mv $@.$$$$.tmp $@



[Wayback] Ralf Hildebrandt

Ralf Hildebrandt is an active and well-known figure in the Postfix community. He’s a systems engineer for T-NetPro, a German telecommunications company and has spoken about Postfix at industry conferences and contributes regularly to a number of open source mailing lists.

Co-author of this book: [Wayback: Book of Postfix State-of-the-Art Message Transport ISBN 9781593270018] (which used to have its own site: [Wayback: The Book of Postfix]

Book of Postfix

State-of-the-Art Message Transport

By Patrick KoetterRalf Hildebrandt

Publisher: No Starch PressRelease Date: March 2005Pages: 496

Best practices for Postfix–the popular alternative to Sendmail. Developed with security and speed in mind, Postfix has become a popular alternative to Sendmail and comes preinstalled in many Linux distributions as the default mailer. The Book of Postfix is a complete guide to Postfix whether used at home, as a mailrelay or virus-scanning gateway, or as a company mailserver. Practical examples show how to deal with daily challenges like protecting mail users from spam and viruses, managing multiple domains, and offering roaming access.

This is a great review of the book: [Wayback] The Book of Postfix (Ralf Hildebrandt, Patrick Koetter)


For my postfix studies… « The Wiert Corner – irregular stream of stuff



Posted in *nix, *nix-tools, bash, Communications Development, Development, Internet protocol suite, Makefile, postfix, Power User, Scripting, SMTP, Software Development | Leave a Comment »

flush deferred messages in mail queue – SysAdmin Tips

Posted by jpluimers on 2021/03/19

[WayBack] flush deferred messages in mail queue – SysAdmin Tips

In Exim:

# exim -qff

In Postfix:

# postfix flush

In Sendmail:

# sendmail -OTimeout.hoststatus=0m -q -v


Posted in *nix, *nix-tools, exim mail, postfix, Power User, sendmail | Leave a Comment »

Inspecting Postfix’s email queue – Tech-G

Posted by jpluimers on 2021/03/08

[WayBack] Inspecting Postfix’s email queue – Tech-G:



postqueue -p


postcat -vq XXXXXXXXXX

Process (flush) the queue:

postqueue -f


postfix flush

Viewing which senders/receivers are in the queue most:

Try with:
– qshape

More specific:
qshape -s deferred | head ===> deferred mails based on SENDER
qshape deferred | head ===> deferred mails based on RECEIVER

Rate limiting: [WayBack] Postfix Configuration Parameters: default_destination_rate_delay


Posted in *nix, *nix-tools, postfix, Power User | Leave a Comment »

Postfix TLS Support

Posted by jpluimers on 2021/02/25

For my link archive:


Posted in *nix, *nix-tools, Communications Development, Development, Internet protocol suite, postfix, Power User, SMTP | Leave a Comment »

Postfix for relaying SMTP, some info about my own configuration

Posted by jpluimers on 2020/03/20

I’ve a bunch of secondary MX servers using postfix (which I like a lot over sendmail). Basically all their configurations are very similar:

  1. To the file /etc/postfix/relay, add a list of domains to relay for, each ending with a space followed by OK as per
    [WayBack] Configure Postfix to relay mail to multiple internal mail servers w/different domains
  2. Run postmap /etc/postfix/relay to update the relay database file.
  3. Ensure that /etc/postfix/ has these settings (note that the FQDN – in the example – isn’t always returned by hostname --fqdn, see below):
    1. inet_interfaces = all
    2. myhostname =
    3. smtpd_helo_required = yes
    4. smtpd_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, reject_unknown_helo_hostname
  4. rcpostfix restart && rcpostfix status

Check the functionality with journalctl -u postfix.

FQDN – how to get myhostname

This usually gives a good indication of your external FQDN, but depending on your network circumstances it might not at all be the FQDN of your machine:

dig +noall +answer +short -x `curl -s` | sed 's/\.$//'

I got there through these StackExchange answers:

Testing with sendEmail

Then test with sendEmail from [WayBack] GitHub – mogaal/sendemail: lightweight, command line SMTP email client, with statements like these

The most recent version is now at [Wayback/] GitHub – zehm/sendEmail: SendEmail is a lightweight, command line SMTP email client.

  • sendEmail -o -f -t -u message-subjetc -s -m message-text
  • sendEmail -o -f -t -u message-subjetc -s -m message-text -v -v -v -v

If you get an error containing 450 4.7.1Helo command rejected: Host not found, then reject_unknown_helo_hostname works, but your -o fqdn= parameter contains an invalid hostname.

More sending examples are in the sendEmail documentation.

If you want to know more about fighting SPAM, then continue at [WayBack] Fighting Spam – What can I do as an: Email Administrator, Domain Owner, or User? – Server Fault


Posted in *nix, *nix-tools, postfix, Power User, sendmail | Leave a Comment »

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