We've all been there - while (1) client process needs to send an email but it fails because it hasn't sent one since yesterday and the server dropped the connection. You don't want to make a new connection every time, so how do you check if your object is still connected? Use the isConnected method of course; oh, except that it doesn't exist... or does it? See below for the undocumented and pseudo-private _NOOP instance method - it is part of the SMTP RFC and thanks to Mr. Barr's attention to detail it is available without having to hack through Net::SMTP's parent classes to issue the command yourself.
#!perl
use strict;
use warnings;

use MIME::Lite;
use Net::SMTP;

our $smtp; # "self-healing" SMTP connection

sub smtp_conn {
    my $server = shift;
    if (!defined $smtp or !$smtp->_NOOP) { # there she is ;)
        $smtp = Net::SMTP->new($server);
    }
    return $smtp;
}

sub send_email {
    my($server,$from,$to,$subject,$body) = @_;
    my $smtp = smtp_conn($server) or return;
    $smtp->mail($from);
    $smtp->to($to);
    my $msg = MIME::Lite->new(
        To      => $to,
        From    => $from,
        Subject => $subject,
        Data    => $body);
    return $smtp->data($msg->as_string);
}

while (1) {
    if ($some_condition eq 'met') {
        send_email(
            'mail.foo.com',
            'larryk@foo.com',
            'a.wee.moose@bar.com',
            'fleeble',
            'blaargh');
    }
    sleep 60;
}

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In reply to Net::SMTP isConnected method by larryk

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