Download Test SMTP

Free for personal, non-commercial use

exe    msi



Online version of Test SMTP

Test SMTP Command line tool

Test SMTP is a command line tool which can be used to diagnose faults with SMTP servers. This self contained tool, which should not require installation on either Windows or Linux platforms, can be run from either a sending SMTP server or receiving SMTP server to reveal many of the common misconfiguration and faults which interrupt mail flow.

Depending on your command line parameters Test SMTP will check the MX records for a domain, PTR (rDNS) records (and that they are not formatted in a way that would trigger anti-spam solutions), check the IP of the SMTP server against DNS Black/Block lists, confirm the SMTP server is accepting connections, is not an open gateway and, if an email address is supplied, that the destination mailbox is available.

This command line tool may be downloaded from our website and executed directly without installation on most Windows and Linux platforms. An MSI installer has been provided for convenience. Once the tool has been downloaded and installed simply open a shell or Command prompt (and navigate to the directory where the executable resides if it has not been placed in a directory included in the system search path or installed using the MSI) and type:

testsmtp [Email Address | SMTP Server IP | Domain Name]

Where Email Address is an email address on the server to be tested. SMTP Server IP is the IP address of the server to be tested or simply the domain to be tested. If an Email address is supplied Test SMTP will also check that the mailbox is ready and waiting to accept mail (Note: No email is sent to the mailbox)

This software is free for personal, non-commercial use.

Command line options:

Usage: testsmtp [OPTION] [EmailAddress | SMTPServerIP | SMTPServerDomain]


-dnsblDo not check DNS Black Lists
+dnsblComma seperated list of DNSBL servers to use
-ptrDo not test PTR record for SMTP Server
-sptrDo not report suspect PTR records
-gatewayDo not test gateway status
+dDomain to test
+ipIP of SMTP Server to test
+portPort to connect to SMTP Server (Default 25)
-vShow version information
-?Show this help text


testsmtp +d

Performs tests on the domain

testsmtp -dnsbl +ip

Performs tests on the SMTP Server at the IP without checking any blacklist servers


Performs tests on the domain and verifies the mailbox is ready to accept inbound mail

Exit status is 0 if no errors where, 1 if tests where not performed or 2 if an error was found

Known Issues (Scheduled to be corrected by 18/03/2011)

  • Hard coded default email address causes some servers to generate an error
  • Long timeout for servers which fail to complete SMTP handshake
  • Early exit seen on the windows build & incorrect result when testing SMTP servers configured by Plesk