--- title: "Manage Postfix Mail Server Queues like a Pro" description: "Understand and manage Postfix email queues like a pro, with examples to fill up queues for better understanding and practice." url: "https://mailmum.io/posts/manage-postfix-mail-server-queues/" image: "https://mailmum.io/images/manage-postfix-mail-server-queues.png" --- # Manage Postfix Mail Server Queues like a Pro ![Manage Postfix Mail Server Queues through shell](https://mailmum.io/images/manage-postfix-mail-server-queues.png) By running a Postfix mail server, you need to know some commands to manage Postfix [mail queues](https://mailmum.io/glossary/email-queue/). With this knowledge, you can manage queues and write simple scripts to accomplish larger tasks. First, I will list the most relevant commands you need for your daily business. Then we will build up real-life examples to understand how these commands work, how to use them, and when they can harm. ## Postfix Mail Queue Commands Postfix has several commands to manage the queues. I list the most important of them and the most used options. ### Postqueue [Postqueue](http://www.postfix.org/postqueue.1.html) is the so-called *Postfix queue control*. We can use this command to display postfix queues in different formats, list enqueued mails, and force Postfix to deliver single deferred emails or all emails at once. ```sh $ postqueue -p # list all enqueued emails in sendmail-style $ postqueue -j # List all queues with messages in JSON format $ postqueue -f # Flush the queue: attempt to deliver all queued mail. $ postqueue -i # Schedule immediate delivery of deferred mail with the specified queue ID. $ man postqueue # show manual/help of postqueue command ``` ### Postcat [Postcat](http://www.postfix.org/postcat.1.html) is used to access queue file contents. You can access the email messages by their ID, which can be listed using *postqueue* command. ```sh postcat -q # show the content of the email message with ID ``` ### Postsuper [Postsuper](http://www.postfix.org/postsuper.1.html) alias *Postfix superintendent* is a tool to manage jobs on the Postfix queue. I use this command only to delete single messages from the queue: ```sh postsuper -d # delete an email message with ID ``` ### Mailq [Mailq](http://www.postfix.org/mailq.1.html) is a *Postfix to Sendmail compatibility interface*. I use it to simply display current queue status. ```sh $ mailq ``` ## Review Postfix Queues To check Postfix mail queues, you have two commands, which show very similar results: ```sh $ mailq Mail queue is empty $ postqueue -p Mail queue is empty ``` If you have nothing in the queues, it's not very interesting, so let's add an email to the queue, which can't be delivered, and try again: ```sh $ mail -s 'testing message subject' someone@gsmail.com <<< 'testing message body' $ mailq -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- 929564780073 257 Fri Feb 12 13:48:24 root someone@gsmail.com $ postqueue -p -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- 929564780073 257 Fri Feb 12 13:48:24 root someone@gsmail.com ``` Now we can see an enqueued email with the corresponding _Queue ID_, which we will need to access, process, and delete single emails inside the queue. **Hint:** As this email can't be delivered, please check the section on how to delete emails from queues. **Hint:** To visually monitor Postfix queues, you can use the [postfix_mailqueue](https://gallery.munin-monitoring.org/plugins/munin/postfix_mailqueue/) [Munin plugin](https://gallery.munin-monitoring.org). ## View single message in Postfix queue by ID To access or view a single enqueued message files, we use [Postcat](http://www.postfix.org/postcat.1.html): ```sh $ postcat -q ``` As the queues are mostly empty, we can enqueue a message, which can't be delivered and check its content: ```sh $ mail -s 'testing message subject' someone@gsmail.com <<< 'testing message body' $ mailq -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- C4CDF478008B 257 Fri Feb 12 14:00:34 root someone@gsmail.com $ postcat -q 57E69478008D postcat -q C4CDF478008B *** ENVELOPE RECORDS deferred/C/C4CDF478008B *** message_size: 462 210 1 0 462 0 message_arrival_time: Fri Feb 12 15:00:17 2021 create_time: Fri Feb 12 15:00:17 2021 named_attribute: rewrite_context=local sender_fullname: root sender: root@mail.yourserver.com *** MESSAGE CONTENTS deferred/C/C4CDF478008B *** Received: by mail.yourserver.com (Postfix, from userid 0) id C4CDF478008B; Fri, 12 Feb 2021 15:00:17 +0100 (CET) To: someone@gsmail.com Subject: testing message subject MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Message-Id: <20210212140017.C4CDF478008B@mail.yourserver.com> Date: Fri, 12 Feb 2021 15:00:17 +0100 (CET) From: root@mail.yourserver.com (root) testing message body *** HEADER EXTRACTED deferred/C/C4CDF478008B *** named_attribute: encoding=8bit named_attribute: dsn_orig_rcpt=rfc822;someone@gsmail.com original_recipient: someone@gsmail.com recipient: someone@gsmail.com *** MESSAGE FILE END deferred/C/C4CDF478008B *** ``` **Attention:** Don't use this function to check the emails of other people. Respect privacy to be respected. Maybe read [SYSTEM ADMINISTRATORS' CODE OF ETHICS @usenix.org](https://www.usenix.org/system-administrators-code-ethics). ## Delete queued mail from the Postfix queue Sometimes we need to delete emails from Postfix queues as account(s) were hacked and someone tried to [abuse](https://mailmum.io/glossary/abuse/) them by sending a massive amount of emails. Sometimes we need to get rid of some test emails a developer or a person attempted to send. [Postsuper](http://www.postfix.org/postsuper.1.html) alias *Postfix superintendent* is a tool to manage jobs on the Postfix queue: ```sh postsuper -d # delete an email message with ID ``` To delete a message, we need first to create a message, to get its Queue ID, and then delete it: ```sh $ mail -s 'testing message subject' someone@gsmail.com <<< 'testing message body' $ mailq -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- E15284780083 462 Fri Feb 12 14:21:19 root@mail.your-server.com (Host or domain name not found. Name service error for name=gsmail.com type=MX: Host not found, try again) someone@gsmail.com $ postsuper -d E15284780083 postsuper: E15284780083: removed postsuper: Deleted: 1 message ``` ### Delete queued messages from a specific email As mass sending emails can built-up queues with thousands of emails, it is hard to delete them by ID. We can use the commands we have used before to do this automatically. The basic idea is to get all enqueued emails, then select the relevant ones and delete them one by one. We will use the Sender/Recipient to get the relevant Queue IDs. First, we will add three emails and then delete them through the example: ```sh $ mail -s 'testing message subject' someone@gsmail.com <<< 'testing message body' $ mail -s 'testing message subject' someone@gsmail.com <<< 'testing message body' $ mail -s 'testing message subject' someone@gsmail.com <<< 'testing message body' $ mailq -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- 9CB0F4780083 462 Fri Feb 12 14:32:17 root@mail.your-server.com (Host or domain name not found. Name service error for name=gsmail.com type=MX: Host not found, try again) someone@gsmail.com 74078478008B 462 Fri Feb 12 14:32:18 root@mail.your-server.com (Host or domain name not found. Name service error for name=gsmail.com type=MX: Host not found, try again) someone@gsmail.com D5E104780090 462 Fri Feb 12 14:32:22 root@mail.your-server.com (Host or domain name not found. Name service error for name=gsmail.com type=MX: Host not found, try again) someone@gsmail.com $ mailq|awk ' /root@mail.your-server.com/ {print $1}' | tr -d '*' | xargs -rn1 postsuper -d postsuper: 9CB0F4780083: removed postsuper: Deleted: 1 message postsuper: 74078478008B: removed postsuper: Deleted: 1 message postsuper: D5E104780090: removed postsuper: Deleted: 1 message $ mailq Mail queue is empty ``` The deletion can be done through a domain name too, as the sender may be forged for a given domain: ```sh $ mailq | awk ' /^[0-9A-F][0-9A-F]*.*some-domain.com$/ {print $1}' | tr -d '*' | xargs -rn1 postsuper -d ``` ### Delete all queued messages **Attention:** Never use this command on production systems, as you can and at some point will delete valid emails, which are in the queue! Sometimes you run a test system and therefore can delete all enqueued emails. You can delete them through [Postsuper](http://www.postfix.org/postsuper.1.html) by running: ```sh $ postsuper -d ALL ``` ## Send all deferred messages Sometimes you need to send (flush) all enqueued emails at once. Enqueueing a larger amount of emails can happen on wrongly configured DNS, getting mails stuck in the outbound queue. Then use [Postqueue](http://www.postfix.org/postqueue.1.html) to send them all at once: ```sh $ postqueue -f ``` There is no output. So don't run this command over and over again. Just give Postfix some time to resend all enqueued emails - especially if there are many of them. **Attention:** Don't run this command repeatedly to deliver emails to users inboxes. These retries can pretty fast hit limits, which may block your server or reduce reputation, which can be long time damage your IP address and your email server to recover from — up to [IP blacklisting](https://mailmum.io/glossary/ip-blacklisting/) of the whole range. ## Summary By using, understanding, and learning those view commands and their most important options, you can manage Postfix queues. Practice on a testing system to understand and get a feeling on possible tasks you have to do if your server is in trouble. With these view commands, you have the right tools/scripts to take action on a growing queue or a hacked user account sending [spam](https://mailmum.io/glossary/spam/) messages from your email server and growing queue. You can even use this know to build a [queue monitoring script](https://mailmum.io/posts/monitoring-postfix-email-queue-with-push-notifications/) for your server(s).