IT_Solution for Learning

This is a program I wrote to benchmark SMTP servers. I started work on this because I need to know which mail server will give the best performance with more than 1,000,000 users. I have decided to release it under the GPL because there is no benefit in keeping the source secret, and the world needs to know which mail servers perform well and which don’t!

At the OSDC conference in 2006 I presented a paper on mail relay performance based on the new BHM program that is now part of Postal.

I have a Postal category on my main blog that I use for a variety of news related to Postal. This post (which will be updated periodically) will be the main reference page for the software. Please use the comments section for bug reports and feature requests.

It works by taking a list of email addresses to use as FROM and TO addresses. I originally used a template to generate the list of users because if each email address takes 30 bytes of storage then 3,000,000 accounts would take 90M of RAM which would be more than the memory in the test machine I was using at the time. Since that time the RAM size in commodity machines has increased far faster than the size of ISP mail servers so I removed the template feature (which seemed to confuse many people).

When sending the mail the subject and body will be random data. A header field X-Postal will be used so that procmail can easily filter out such email just in case you accidentally put your own email address as one of the test addresses. ;)

I have now added two new programs to the suite, postal-list, and rabid. Postal-list will list all the possible expansions for an
account name (used for creating a list of accounts to create on your test server). Rabid is the mad Biff, it is a POP benchmark.

Postal now adds a MD5 checksum to all messages it sends (checksum is over the subject and message body including the “\r\n” that ends each line of text in the SMTP protocol). Rabid now checks the MD5 checksum and displays error messages when it doesn’t match.

I have added rate limiting support in Rabid and Postal. This means that you can specify that these programs send a specific number of messages and perform a specific number of POP connections per minute respectively. This should make it easy to determine the amount of system resources that are used by a particular volume of traffic. Also if you want to run performance analysis software to determine what the bottlenecks are on your mail server then you could set Postal and Rabid to only use half the maximum speed (so the CPU and disk usage of the analysis software won’t impact on the mail server).

I will not release a 1.0 version until the following features are implemented:


* Matching email sent by Postal and mail received by BHM and Rabid to ensure that each message is delivered correctly (no repeats and no corruption)

* IMAP support in Rabid that works

* Support for simulating large numbers of source addresses in Postal. This needs to support at least 2^24 addresses so it is entirely impractical to have so many IP addresses permanently assigned to the test machine.

* Support for simulating slow servers in Postal and BHM (probably reducing TCP window size and delaying read() calls)

* Making BHM simulate the more common anti-spam measures that are in use to determine the impact that they have on list servers

* Determining a solution to the problem of benchmarking DNS servers. This may mean just including documentation on how to simulate the use patterns of a mail server using someone else’s DNS benchmark, but may mean writing my own DNS benchmark.

download link: http://www.coker.com.au/postal/postal-0.70.tgz

reference: http://doc.coker.com.au/projects/postal/