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Using Postal for Performance Testing

Nathan Salt -


I would like to know how many messages Atmail can receive or send, and how many concurrent users can be served via POP3 or IMAP.


  • On-Premise Server + WebMail Installations: Version 6.0 > Current Version


You're a good Systems Administrator who likes to know the capability of your systems.


You can test the capability of your system using an application called Postal

  1. Download and install Postal.
    wget ""
    tar xvfz postal-0.70.tgz
    cd postal-0.70
    ./configure && make && make install
  2. Generate a list of users to import into Atmail for testing. It will be much more efficient to affix a common prefix to the accounts unique to the testing. This will make the deletion easier in the future. A list of about 100 users should be adequate. The more users, the wider the search parameters, and the more accurate the test will be. For example:
    testing-user1, password,
    testing-user2, password,
    testing-user3, password,
    testing-user4, password,
  3. Import the userlist into Atmail. For this example, we will use the filename "userlist.txt" and user "admin":
    cd /usr/local/atmail/webmail/utilities/migration/
    php migrate-users-csv.php userlist.txt admin
  4. You will need to reformat the file to suit the one that postal requires. This command will generate a file based on your previous list:
    cat userlist.txt | sed 's/,/ /g' | awk '{print $1 "@" $3 ","$2}' > userlist_postal.txt 
  5. You can now execute this command to test SMTP connections. This command creates a test where messages can vary from 1-10 KB, a maximum of 24,000 messages are sent a minute, with five threads, and 10 maximum messages per connection. Replace [server ip] with the IP of the Atmail server.

    This command will generate messages in intervals of one minute each. 10 minutes should be a good sample size. It will list the amount of messages accepted, sent, and errored out during that period. In the case that you get an error message during this test period, it is likely caused by SMTP limits that Atmail imposes on a per-IP basis. You may need to set the values in the Atmail WebAdmin to accomodate the test (considering that you are sending emails from a singular IP).

    Press Control-C to terminate the test:

    postal -m 10 -r 24000 -t 5 -c 5 -s 0 [server ip] userlist_postal.txt
  6. To test POP3/IMAP, run the following command. This will create a test with five threads, 5 messages a connection, with a maximum of 24,000 connections a minute. As with above, This command will generate messages in intervals of one minute each. 10 minutes should be a good sample size.
    rabid -p 5 -c 5 -r 24000 -s 0 [server ip] userlist_postal.txt


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