Add Servers/Email/iRedMail/Query SMTP Outgoing Queue.md

Servers/Email/iRedMail/Query SMTP Outgoing Queue.md

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+## Purpose
+You may need to troubleshoot the outgoing SMTP email queue / active sessions in iRedMail for one reason or another.  This can provide insight into the reason why emails are not being delivered, etc.
+
+### Overall Queue Backlog
+You can run the following command to get the complete backlog of all email senders in the queue.  This can be useful for tracking the queue's "drainage" over-time.
+
+```sh
+postqueue -p | awk '/^[A-F0-9]/ {id=$1} /from=<[^>]+>/ && $0 !~ /from=<>/ {print id; exit}'
+```
+
+!!! example "Example Output"
+    10392 problematic@bunny-lab.io
+    301 prettybad@bunny-lab.io
+    39 infrastructure@bunny-lab.io
+    20 nicole.rappe@bunny-lab.io
+
+### Investigating Individual Emails
+You can run the following command to read detailed information on any specific queued SMTP message:
+
+```sh
+postqueue -p
+postcat -vq 4dgHry5LZnzH6x08 # (1)
+```
+
+1.  Example message ID gathered from the previous `postqueue -p` command.