I recently noticed that the mail queue on a busy mail server i maintain was becoming disturbingly long at times.

Graphing a mail queue can be done with a little script and some cacti mojo.

Firstly, create a script that outputs the length of the queue which will be understood by cacti. The output needs to look something like

mailq:17

Ive chosen to write a script in python called check_mailq which you can find here.

Within cacti, go to the Console and add a 'Data Input Method' with the following attributes.

Name: Get mailq
Input Type: Script/Command
Input String: [path to your mailq script]

Ive used the following path for my Input String

/usr/local/cacti/bin/check_mailq

Within the 'Data Input Method' the 'Input Fields' stays empty though you need to create an 'Output Field' with the following attributes.

Field [Output]: mailq
Friendly Name: mailq
Update RRD File: [checked]

Save the 'Data Input Method' and then create a 'Data Template' using the following attributes

Data Templates
Name: mailq

Data Source
Name: |host_description| - mailq
Data Input Method: mailq
Data Source Item: mailq
Data Source Type: GAUGE
Output Field: mailq - mailq

Save the 'Data Template' and create a 'Data Source'.

Select Data Template: mailq
Host: [select your host]

Save the 'Data Source' and create a graph with 'Graph Management'

Selected Graph Template: None
Host: [select your host]
Title: [insert your hostname] - mailq

Click create then click add within the 'Graph Items' section

Data Source: [your hostname] - mailq (mailq)
Color: 00FF00
Graph Item Type: AREA
Text Format: queued emails

Click create, wait 10 minutes and a graph of your mail queue should appear within the Graphs section of cacti.