check_email_delivery

With the german locale check_smtp_send creates a date header that may contain characters specific to locale as in my case an ä in Mär (abbreviated german march)

Date: Di, 2 Mr 2021 22:42:57 +0100 (CET)

I could fix this by changing locale before running check_smtp_send

We've used this package to make sure our email environment is delivering messages in a timely fashion. It's a great tool. However, it hasn't been updated in some time.

check_smtp_send depends on Net::SMTP::TLS which is no longer maintained and breaks with new IO::Socket::SSL. That's when you'll see:

invalid SSL_version specified

The fix is to change check_smtp_send to use Net::SMTP which now directly supports STARTTLS.

Patch:

diff --git a/check_smtp_send b/check_smtp_send
index ade0fe3..9be3869 100755
--- a/check_smtp_send
+++ b/check_smtp_send
@@ -85,7 +85,6 @@ if( $smtp_server eq "" && scalar(@mailto) == 1 ) {
my @required_module = ();
push @required_module, 'Net::SMTP::SSL' if $ssl;
push @required_module, ('MIME::Base64','Authen::SASL') if $ssl && $username;
-push @required_module, 'Net::SMTP::TLS' if $tls;
push @required_module, 'Net::SMTP_auth' if $auth_method and not $tls; # whereas if auth_method and tls we use TLS_auth, which is included in this script!
push @required_module, 'Text::Template' if $template;
push @required_module, 'Net::DNS' if $mx_lookup;
@@ -141,7 +140,7 @@ if( $mx_lookup ) {
}

# connect to SMTP server
-# create the smtp handle using Net::SMTP, Net::SMTP::SSL, Net::SMTP::TLS, or an authentication variant
+# create the smtp handle using Net::SMTP, Net::SMTP::SSL, or an authentication variant
my $smtp;
eval {
if( $tls and $auth_method ) {
@@ -154,7 +153,7 @@ eval {
}
elsif( $tls ) {
$smtp_port = $default_smtp_tls_port unless $smtp_port;
- $smtp = Net::SMTP::TLS->new($smtp_server, Timeout=>$timeout, Port=>$smtp_port, User=>$username, Password=>$password);
+ $smtp = Net::SMTP->new($smtp_server, Timeout=>$timeout, Port=>$smtp_port, User=>$username, Password=>$password, starttls=>1);
if( $smtp ) {
my $message = oneline($smtp->message());
die "cannot connect with TLS: $message" if $smtp->code() =~ m/53d/;

The "delivery email" script doesn't not run if you have not installed the "IMAPClient" software, that I'm unable to find into yum.

The plugin itself works just great. There is however a minor issue. In my case the plugin identifies itself to the remote server with ' HELO localhost.localdomain'. My server does not accept this is as part of antispam solution.

The fix is to add "Hello=>'your.nagios.server'" to the new class instance definition:

$smtp = Net::SMTP->new($smtp_server, Port=>$smtp_port, Timeout=>$timeout,Debug=>$smtp_debug, Hello=>'nagios.example.com');

Great plugin. However in check_smtp_send, I noticed a small bug because of which the date timestamp was not being set properly. Here is the fix for it - In check_smtp_send on line 349, change "gmtime" to "localtime". This will set the correct timestamp in the sent mails.