check_smtp_send(7) connects to an SMTP server and sends a message


check_smtp_send -vV
check_smtp_send -?
check_smtp_send --help


--warning <seconds>
Warn if it takes longer than <seconds> to connect to the SMTP server. Default is 15 seconds. Also known as: -w <seconds>
--critical <seconds>
Return a critical status if it takes longer than <seconds> to connect to the SMTP server. Default is 30 seconds. Also known as: -c <seconds>
--timeout <seconds>
Abort with critical status if it takes longer than <seconds> to connect to the SMTP server. Default is 60 seconds. The difference between timeout and critical is that, with the default settings, if it takes 45 seconds to connect to the server then the connection will succeed but the plugin will return CRITICAL because it took longer than 30 seconds. Also known as: -t <seconds>
--hostname <server>
Address or name of the SMTP server. Examples:, localhost,

If not provided, and if there is only one --mailto address, the script will automatically look up the MX record for the --mailto address and use that as the hostname. You can use this to check that your MX records are correct. When omitting the --hostname option, it doesn't really make sense to specify --port, --username, or --password but you can still do so and they will have their normal effect. To look up the MX records you need to have the module Net::DNS and Email::Address installed.

Also known as: -H <server>

--port <number>
Service port on the SMTP server. Default is 25 for regular SMTP, 465 for SSL, and 587 for TLS. Also known as: -p <number>
Enable TLS/AUTH protocol. Requires Net::SMTP::TLS, availble on CPAN.

When using this option, the default port is 587. You can specify a port from the command line using the --port option.

Use the notls option to turn off the tls option.

Also, you may need to fix your copy of Net::SMTP::TLS. Here is the diff against version 0.12:

 <      $me->_command(sprintf("AUTH PLAIN %S",
 >      $me->_command(sprintf("AUTH PLAIN %s",
Enable SSL protocol. Requires Net::SMTP::SSL and Authen::SASL, availble on CPAN.

When using this option, the default port is 465. You can override with the --port option.

Use the nossl option to turn off the ssl option.

--auth <method>
Enable authentication with Net::SMTP_auth (sold separately). For example, try using --auth PLAIN or --auth CRAM-MD5.
--username <username>
--password <password>
Username and password to use when connecting to SMTP server. Also known as: -U <username> -P <password>
--body <message>
Use this option to specify the body of the email message. If you need newlines in your message, you might need to use the --stdin option instead.
--header <header>
Use this option to set an arbitrary header in the message. You can use it multiple times.
Grab the body of the email message from stdin.
--mailto [email protected]
You can send a message to multiple recipients by repeating this option or by separating the email addresses with commas (no whitespace allowed):

$ check_smtp_send -H --mailto [email protected],[email protected] --mailfrom [email protected]

SMTP SEND OK - 1 seconds

--mailfrom [email protected]
Use this option to set the ``from'' address in the email.
Enable (or disable) processing of message body and headers. Requires Text::Template.

Use this option to apply special processing to your message body and headers that allows you to use the results of arbitrary computations in the text. For example, you can use this feature to send a message containing the hostname of the machine that sent the message without customizing the plugin configuration on each machine.

When you enable the --template option, the message body and headers are parsed by Text::Template. Even a message body provided using the --stdin option will be parsed. See the Text::Template manual for more information, but in general any expression written in Perl will work.

There is one convenience function provided to you, trim, which will remove leading and trailing whitespace from its parameter. Here's an example:

 check_smtp_send -H --mailto [email protected] --mailfrom [email protected] 
 --template --body 'hello, this message is from {use Sys::Hostname; hostname}' 
 --header 'Subject: test message from {trim(`whoami`)}'
--expect-response <code>
Use this option to specify which SMTP response code should be expected from the server after the SMTP dialog is complete. The default is 250 (message accepted).

Also known as: -E <code>

Use the Time::HiRes module to measure time, if available.
Display additional information. Useful for troubleshooting.

One --verbose will show extra information for OK, WARNING, and CRITICAL status.

Use one --verbose together with --version to see the default warning and critical timeout values.

Three --verbose (or -vvv) will show debug information, unless you're using --tls because Net::SMTP::TLS does not have a Debug feature.

Also known as: -v

Display plugin version and exit. Also known as: -V
Display this documentation and exit. Does not work in the ePN version. Also known as: -h
Display a short usage instruction and exit.


Send a message with custom headers

$ check_smtp_send -H --mailto [email protected] --mailfrom [email protected] --body 'Homeruns 5' --header 'Subject: Hello, world!' --header 'X-Your-Header: Yes'

SMTP SEND OK - 1 seconds


Complies with the Nagios plug-in specification:
 0              OK                      The plugin was able to check the service and it appeared to be functioning properly

 1              Warning         The plugin was able to check the service, but it appeared to be above some ``warning'' threshold or did not appear to be working properly

 2              Critical        The plugin detected that either the service was not running or it was above some ``critical'' threshold

 3              Unknown         Invalid command line arguments were supplied to the plugin or the plugin was unable to check the status of the given hosts/service


Nagios plugin reference:

This plugin does NOT use Nagios DEFAULT_SOCKET_TIMEOUT (provided by as $TIMEOUT) because the path to must be specified completely in this program and forces users to edit the source code if their install location is different (if they realize this is the problem). You can view the default timeout for this module by using the --verbose and --version options together. The short form is -vV.

Other than that, it attempts to follow published guidelines for Nagios plugins.


 Wed Oct 29 14:05:00 PST 2005
 + version 0.1
 Wed Nov  9 15:01:48 PST 2005
 + now using an inline PluginReport package to generate the report
 + added stdin option
 + copyright notice and GNU GPL
 + version 0.2
 Thu Apr 20 16:00:00 PST 2006 (by Geoff Crompton <[email protected]>)
 + added bailing if the $smtp->to() call fails
 + added support for mailto recipients separated by commas
 + version 0.2.1
 Tue Apr 24 21:17:53 PDT 2007
 + moved POD text to separate file in order to accomodate the new embedded-perl Nagios feature
 + version 0.2.3
 Fri Apr 27 20:26:42 PDT 2007
 + documentation now mentions every command-line option accepted by the plugin, including abbreviations
 + version 0.3
 Sun Oct 21 10:34:14 PDT 2007
 + added support for TLS and authentication via the Net::SMTP::TLS module. see --tls option.
 + version 0.4
 Sun Oct 21 13:54:26 PDT 2007
 + added support for SSL via the Net::SMTP::SSL module. see --ssl option.
 + port is no longer a required option. defaults to 25 for regular smtp, 465 for ssl, and 587 for tls.
 + added port info to the "could not connect" error message
 + version 0.4.1
 Tue Dec  4 07:42:32 PST 2007
 + added --usage option because the official nagios plugins have both --help and --usage
 + added --timeout option to match the official nagios plugins
 + fixed some minor pod formatting issues for perldoc
 + version 0.4.2
 Mon Feb 11 19:09:37 PST 2008
 + fixed a bug for embedded perl version, variable "%status" will not stay shared in load_modules
 + version 0.4.3
 Mon May 26 09:12:14 PDT 2008
 + fixed warning and critical messages to use "more than" or "less than" instead of the angle brackets, to make them more web friendly
 + version 0.4.4
 Wed Jul  2 07:12:35 PDT 2008
 + added --expect-response option submitted by Christian Kauhaus <[email protected]>
 + added support for authentication via Net::SMTP_auth. see --auth option.
 + version 0.4.5
 Sun Oct  5 15:18:23 PDT 2008
 + added error handling for smtp server disconnects ungracefully during QUIT ( does)
 + version 0.4.6
 Thu Oct  1 12:09:35 PDT 2009
 + added --template option to allow arbitrary substitutions for body and headers, and provided one convenience function for trimming strings
 + added performance data for use with PNP4Nagios!
 + version 0.5.0
 Thu Oct  8 11:17:04 PDT 2009
 + added more detailed error messages when using --verbose
 + version 0.5.1
 Tue Feb  9 12:14:49 PST 2010
 + added support for combining --auth with --tls using a subclass of Net::SMTP::TLS submitted by Brad Guillory; please note that to use the "PLAIN" authentication type you need to patch your Net::SMTP:TLS because it has a bug in sub auth_PLAIN (sprintf %S instead of %s)
 + version 0.5.2
 Mon Jan  3 10:39:42 PST 2011
 + added default Date and Message-ID headers; Date header uses POSIX strftime and Message-ID header uses hostname command to get localhost name
 + version 0.7.0
 Fri May  6 08:35:09 AST 2011
 + added --hires option to enable use of Time::Hires if available
 + version 0.7.1
 Wed Jul  6 19:18:26 AST 2011
 + the --hostname is now optional; if not provided the plugin will lookup the MX record for the --mailto address (requires Net::DNS)
 + version 0.7.2
 Tue Dec 13 09:24:04 PST 2011
 + separated authentication errors from connection errors
 + version 0.7.3


Jonathan Buhacoff <[email protected]>


 Copyright (C) 2005-2011 Jonathan Buhacoff
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 3 of the License, or
 (at your option) any later version.
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <>.