Summary
A variety of tools and techniques can simulate email traffic and stress-test Postfix clusters. Postfix offers `smtp-sink` for basic stress testing, but it lacks real-world accuracy. Tools like `swaks`, JMeter, and Floodnsmtp offer more sophisticated traffic simulation. Custom Python scripts give precise control over email generation. Dummy SMTP servers like MailHog capture traffic without sending actual emails. Simulating sending to blocklist honeypots tests deliverability. When using real emails, consider the impact on regular mail servers and spam issues.
Key findings
- Postfix smtp-sink: A built-in tool for basic stress testing but limited in simulating real-world conditions.
- Swaks: Command-line tool for sending emails and measuring processing time, useful for load testing.
- JMeter: Apache JMeter's SMTP sampler simulates email traffic for load and stress testing.
- Python Scripts: Allows custom control over email volume and content for simulating traffic.
- MailHog: Dummy SMTP server captures emails without sending, preventing spam issues.
- Floodnsmtp: Designed for easy simulation of network behavior by sending a large volume of emails.
- Nping: Crafts custom SMTP packets to probe Postfix servers and analyze their behavior.
- Honeypot Simulation: Simulating sending to blocklist honeypots provides insights into deliverability and blocklisting.
- Temporary Mail Server: A separate temporary server to receive emails during a test so your primary inbound server isn't affected.
Key considerations
- Real-World Accuracy: Ensure the simulation reflects real-world delivery conditions, including DNS and delivery latency.
- Impact on Production: Sending real emails during testing can impact production mail servers and reputation.
- Spam Filters: Avoid triggering spam filters when generating test traffic.
- Content Variability: Controlling sending rate and varying email content is important for effective stress testing.
- Inbound Mail Handling: Consider the inbound email handling for stress tests. Will the mail be dropped? Stored? Analysed?
What email marketers say
8 marketer opinions
Various tools and methods exist to simulate email traffic and stress test a Postfix cluster. These range from simple command-line tools like `swaks` and the `mail` command, to dedicated traffic generators and dummy SMTP servers like MailHog. Custom Python scripts offer flexibility in controlling email volume and content. When sending actual emails, one must consider the impact on the regular mail server and potential spam issues. Stress testing can also be simulated using honeypots.
Key opinions
- Swaks: Swaks can be used to send emails to Postfix and measure processing time to identify performance bottlenecks.
- Python Scripts: Custom Python scripts allow precise control over email volume and content variability during stress tests.
- MailHog: MailHog and other dummy SMTP servers can capture generated email traffic for analysis without sending actual emails.
- Mail Command: mail command combined with shell scripts can be used to send system messages for stress testing.
- Traffic Simulators: Multithreaded email senders can simulate traffic loads for Postfix setups.
- Temporary Mail Server: Use a separate temporary server to receive emails during a test so your primary inbound server isn't affected.
Key considerations
- Impact on Regular Mail Server: Sending actual emails during stress testing can affect the regular mail server's performance.
- Potential Spam Issues: Sending a large volume of test emails can trigger spam filters and negatively impact sender reputation.
- Traffic Control: Controlling sending rate and content variability is crucial for realistic simulation and avoiding false positives.
- Inbound Email Handling: Consider the inbound email handling for stress tests. Will the mail be dropped? Stored? Analysed?
Marketer view
Email marketer from Email Geeks shares that if you send actual emails, you're also stress testing your regular mail server, which might cause trouble. Also shares that in the past, he spun up a temporary mail server to handle inbound mail and just delete _most_ of them immediately, then set his outbound mail server to use that receiver as a gateway.
24 Mar 2024 - Email Geeks
Marketer view
Email marketer from LinuxQuestions.org recommends a simple tool called 'mail бомбер' that can be used to quickly generate lots of test traffic, for basic traffic simulation.
9 Jul 2021 - LinuxQuestions.org
What the experts say
3 expert opinions
Postfix includes `smtp-sink` for accepting and discarding mail, useful for basic stress testing but doesn't reflect real-world performance due to ignoring delivery and DNS latency. Simulating sending to blocklist honeypots offers insights into how your mail infrastructure reacts to deliverability challenges and potential blocklisting triggers.
Key opinions
- smtp-sink: Postfix's `smtp-sink` can accept and discard large volumes of email for basic stress testing.
- smtp-sink Limitations: `smtp-sink` does not simulate real-world conditions due to the lack of delivery and DNS latency consideration.
- Honeypot Simulation: Simulating sending to blocklist honeypots can provide insights into deliverability challenges and blocklisting triggers.
Key considerations
- Real-World Simulation: Ensure your testing method accurately reflects real-world email delivery conditions for meaningful results.
- Infrastructure Reaction: Consider how your infrastructure will react to deliverability challenges.
- Blocklisting Triggers: Understand potential blocklisting triggers.
Expert view
Expert from Word to the Wise, Laura Atkins, explains that you can simulate sending emails to blocklist honeypots as a form of stress testing. This helps understand how your mail infrastructure reacts and what triggers blocklisting, simulating real-world deliverability challenges.
4 Oct 2021 - Word to the Wise
Expert view
Expert from Email Geeks explains that using `smtp-sink` won’t bear any resemblance to real world performance, though, as it doesn’t take into account delivery or dns latency.
3 Dec 2023 - Email Geeks
What the documentation says
4 technical articles
Several tools and methods are available for simulating email traffic and stress testing a Postfix cluster. Postfix's built-in smtp-sink accepts and discards emails without logging, useful for basic stress testing. Apache JMeter can simulate traffic via its SMTP sampler. Floodnsmtp facilitates network behavior simulation with high email volume, and Nping allows crafting SMTP packets for server probing and response analysis.
Key findings
- smtp-sink: Postfix's smtp-sink is suitable for basic stress testing and content filter integration testing.
- Apache JMeter: Apache JMeter's SMTP sampler allows simulating email traffic for load and stress testing purposes.
- Floodnsmtp: Floodnsmtp aids in simulating network behavior with high volumes of generated emails from command-line options or files.
- Nping: Nping helps craft SMTP packets and probe Postfix servers, enabling response time analysis and behavior observation.
Key considerations
- Simulation Accuracy: Ensure tools used provide a realistic simulation of network conditions and email traffic patterns.
- Logging: Consider logging capabilities of tools used, as some may not provide detailed logs for analysis.
- Customization: Evaluate the degree of customization needed and whether the tool supports it.
Technical article
Documentation from Postfix.org explains that the smtp-sink(8) program implements a Postfix SMTP server that produces no output, not even in the logs. This program is useful for stress-testing Postfix, or for testing Postfix integration with content filters.
22 Feb 2023 - Postfix.org
Technical article
Documentation from Apache.org details how JMeter can be configured to send emails using SMTP sampler, allowing simulation of email traffic for load and stress testing.
19 Nov 2024 - Apache.org
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