nmap --script smtp-open-relay -p 25 your-server.com Use rate limiting to block IPs that make too many connections or attempts within a short time. For Postfix:
| Tool | License | Platform | Key Feature | |------|---------|----------|--------------| | (with smtp-open-relay script) | GPL | Cross-platform | Industry standard | | smtp-user-enum | GPL | Linux | Enumerate users via VRFY/EXPN | | Metasploit (auxiliary/scanner/smtp/smtp_relay) | BSD | Cross-platform | Full pentest framework | | swaks | GPL | Linux/macOS | Swiss army knife for SMTP | Speed Smtp Scanner V2.5 Free Download
| Feature | Description | |---------|-------------| | | Scans thousands of IPs per second using adjustable thread counts (up to 500+). | | CIDR & Range Support | Accepts single IPs, IP ranges (e.g., 192.168.1.1-255), or CIDR notation (e.g., 203.0.113.0/24). | | SMTP Authentication Testing | Supports LOGIN, PLAIN, CRAM-MD5 mechanisms; includes built-in weak password lists. | | Open Relay Check | Tests using common relay test emails (e.g., test@example.com to test@test.com ). | | Proxy Integration | Can route scans through SOCKS4/5 or HTTP proxies to hide the source IP. | | Result Export | Saves working servers, open relays, and cracked credentials to .txt or .csv files. | | Banner Grabbing | Retrieves SMTP server banners (e.g., ESMTP Exim, Microsoft ESMTP). | | Geo-IP Filtering | Option to target specific countries or exclude certain ranges. | | Lightweight & Portable | Under 2 MB, no installation required – runs directly from a USB drive. | How Speed SMTP Scanner Works: A Technical Deep Dive To use the tool effectively (or defend against it), you must understand its internal logic. Here is a step-by-step breakdown of a typical scanning session: Step 1: Target Acquisition The user provides a list of IP addresses or ranges. For example: 185.0.0.0/16 . The scanner generates all possible IPs in that range. Step 2: TCP Connect Scan on Port 25 Using raw sockets or WinSock, the scanner attempts a TCP handshake with each IP on port 25. If the connection is successful, the server is marked as "SMTP Alive." Step 3: SMTP Greeting & EHLO The scanner sends an EHLO scanner.local command. The server responds with a banner. Based on the banner, the scanner identifies the mail server software (e.g., Exchange, Postfix, Sendmail). Step 4: Open Relay Test The scanner issues the following commands: nmap --script smtp-open-relay -p 25 your-server
Introduction In the world of email marketing, server administration, and cybersecurity testing, tools that interact with Simple Mail Transfer Protocol (SMTP) are essential. Among the most talked-about utilities in underground forums and tech communities is the Speed SMTP Scanner V2.5 . Promising rapid detection of open relays, live mail servers, and SMTP authentication vulnerabilities, this tool has gained notoriety. | | SMTP Authentication Testing | Supports LOGIN,
smtpd_client_connection_rate_limit = 10 smtpd_client_message_rate_limit = 10 Tools like Postgrey or milter-greylist temporarily reject unknown senders. Legitimate mail servers retry after a delay; automated scanners rarely do. 4. Use Fail2Ban Monitor your mail logs for repeated failed AUTH attempts or relay tests, then block offending IPs automatically. 5. Run a Honeypot Set up a fake SMTP server (e.g., using honeyd or T-Pot ) that logs every connection. Submit scanner IPs to AbuseIPDB and your ISP. Frequently Asked Questions (FAQ) Q1: Is Speed SMTP Scanner V2.5 legal to download? A: The tool itself is not illegal in most countries. However, using it against any system without authorization is illegal. Simply possessing it can be used as evidence of malicious intent. Q2: Can I use it on my own home server? A: Yes, if you own the server and the network it resides on (including any cloud VM you have purchased). But never scan your ISP’s infrastructure or shared hosting neighbors. Q3: Does it work on Windows 10/11? A: Older versions may have compatibility issues. Run in Windows 7 compatibility mode or inside a virtual machine (VMware, VirtualBox) without network access to the host. Q4: Is there a macOS or Linux version? A: No, the original "Speed SMTP Scanner" is Windows-only. For Linux, use the alternatives listed above. Q5: I found a version that says "Cracked" or "Keygen". Is it safe? A: Absolutely not. Cracks and keygens are the #1 vector for malware. Assume any executable from a torrent or crack site is dangerous. Conclusion: Think Before You Download The search for "Speed SMTP Scanner V2.5 Free Download" often begins with curiosity—whether for educational purposes, email marketing automation, or security testing. But the reality is that this tool exists in a legal and ethical gray zone. While its technical capabilities are interesting from a network protocol perspective, the risks far outweigh the benefits for 99% of users.
