#!/usr/bin/perl
###############################################
## Mail Latency - Check Email
##
## v1.0 - 10/15/2007 - Walt Howd
##
## This script is designed to monitor  
## email servers and report e-mail latency.
##
## This script works in conjunction with another
## that connects to an external mail server
## and sends a test message containing the UNIX
## timestamp in the message body. 
##
## This script checks the local mail server
## via POP and then can report for each mail
## server in the message headers how long it 
## took in seconds for the message to arrive.
##
## Usage:
## ./checkEmail.pl SERVERNAME --measure=METHOD
##
## ./checkEmail mail --measure=absolute
##
## ./checkEmail mail.domain.com --measure=relative
##
## This will give you the average time in 
## seconds for mail server supplied on the 
## command line. This could be the end server
## you are accessing via POP or any intermediary
## mail servers along the path. 
##
## The second option lets you specify if you want
## the time delay from the last non local mail server
## as distinguished by $dnsDomain (servers matching your
## dns suffix). If not specified the script will report
## the absolute time from when the message was sent
## to when the message arrived.
##
## After checking and reporting the average time
## the messages with the matching subject line
## are deleted.
##
## Copyright Walt Howd
##
## 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 2 of the License, or
## 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
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## 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, write to the Free Software
## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
##
###############################################

###############################################
## Configuration Variables
###############################################  
$dnsDomain                      = "domain.com";
$mailServer                     = "mail.domain.com";
$mailPort                       = "995";
$mailUser                       = "username";
$mailPassword                   = "password";
$mailSubject                    = "MailLatency";
$mailSSL                        = "true";
$noMatchTime                    = 0;

###############################################
## Load Modules
###############################################
use Mail::POP3Client;
use Date::Parse;
use Getopt::Long;

###############################################
## Usage options
###############################################
GetOptions("measure:s" => \$measure, "debug:s" => \$debug);
$serverToCheck = $ARGV[0];
if(!$serverToCheck || !$measure && (!($measure =~ /absolute/gi) || !($measure =~ /relative/gi)) ) {
    die("\nUsage:\n./checkEmail SERVERNAME --measure=absolute\n\n./checkEmail SERVERNAME --measure=relative\n\n");
}   

###############################################
## Connect to POP Server
###############################################    
$pop = new Mail::POP3Client( USER     => $mailUser,
                             PASSWORD => $mailPassword,
                             HOST     => $mailServer,
                             USESSL   => $mailSSL,
                           );
                           
###############################################
## Examine each message
###############################################                           
for ($i = 1; $i <= $pop->Count(); $i++) {
    foreach ( $pop->Head( $i ) ) {
        
        ###############################################
        ## Only examine messages with this matching
        ## subject
        ###############################################           
        if($_ =~ /^Subject:\s+$mailSubject - $serverToCheck - $measure/i) {     
                    
            ###############################################
            ## Loop through each line of the mail header
            ###############################################               
            foreach ( $pop->Head( $i ) ) {
                chomp();
                
                ###################################################
                ## Look for the text "Received: by mail.server.net
                ## to see what mail server the next time stamp we 
                ## see belongs to 
                ###################################################                         
                if($_ =~ /(by\s)(\S+\.\S+\.\w{3}|\d{1,2,3}\.\d{1,2,3}\.\d{1,2,3}\.\d{1,2,3})/gi) {                        
                    $smtpServer = $_;
                    $smtpServer =~ s/(^.*?)(by\s)(\S+\.\S+\.\w{3}|\d{1,2,3}\.\d{1,2,3}\.\d{1,2,3}\.\d{1,2,3})(.*$)/$3/gi
                }   
                    
                ###################################################
                ## See if this line contains a recognized date 
                ## if so, then convert that date to a timestamp and  
                ## see what the difference is from the time the 
                ## message was orignally sent. The original time
                ## is a UNIX timestamp in the message body.
                ##
                ## Sorry for the ridiculous regexs.
                ###################################################                     
                if($_ =~ /(Sun|Mon|Tue|Wed|Thu|Fri|Sat)(,\s+\d+\s+?)(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)(\s+\d+?)(\s+\d+:\d+:\d+)(\s+[A-Z]{3}|\s+.\d+)/gi) {
                    $bodyTS     = $pop->Body( $i );
                    chomp($bodyTS);
                    
                    $recTime    = $_;
                    $recTime    =~ s/(^.*?)(Sun|Mon|Tue|Wed|Thu|Fri|Sat)(,\s+\d+\s+?)(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)(\s+\d+?)(\s+\d+:\d+:\d+)(\s+[A-Z]{3}|\s+.\d+)(.*$)/$2$3$4$5$6$7/gi;
                    $recTS      = Date::Parse::str2time($recTime, 'GMT');
                    
                    $diff       = $recTS - $bodyTS;
                    
                    ###################################################
                    ## If this time belongs to the mail server supplied
                    ## on the command line then store the time so we can
                    ## later return an average
                    ###################################################                     
                    if($smtpServer =~ /$serverToCheck/gi)  {

                        if($debug) {
                            print "Processing server $smtpServer - $serverToCheck\n\n";
                        }
                        
                        $match                  = 1;
                        $foundFinalMailServer   = 1;
                        $totTime                = $totTime + $diff;
                        $totMatch++;                        
                    }
                    
                    ###################################################
                    ## Record the delay on the last non local mail 
                    ## server as determined by non matching dns suffix. 
                    ###################################################                       
                    if(!($smtpServer =~ /$dnsDomain/gi) && !$foundLastNonLocalMailServer) {                        
                        $foundLastNonLocalMailServer    = 1;
                        $totLastNonLocalTime            = $totLastNonLocalTime + $diff;
                        $totLastNonLocalMatch++;
                    }
                    
                    if($debug) {
                        print "Server:\t\t$smtpServer\nDate:\t\t$_\nRegEx:\t\t$recTime\nTimestamp:\t$recTS\nBodyStamp:\t$bodyTS\nAbsDiff:\t$diff\n\n";                      
                    }
                }                
            }   
            
            ###################################################
            ## Delete any messages in this account that matched
            ## our subject line and clear our message flags
            ###################################################             
            $pop->Delete( $i );    
            $foundLastNonLocalMailServer    = 0;  
            $foundFinalMailServer           = 0;
                     
            if($debug) {         
                print "Resetting final found server\n\n";
            }
        }         
    }
}

###############################################
## If no matches are found then return ZERO
##
## If matches are found, average them out for
## mail server supplied on the command line
###############################################  
if(!($match)) {
    print "$noMatchTime\n";
} else {
    $absAvg             = int($totTime / $totMatch);
    $lastNonLocalAvg    = int($totLastNonLocalTime / $totLastNonLocalMatch);
    $relAvg             = $absAvg - $lastNonLocalAvg;
        
    if($debug) {
        print "AbsAvg:\t\t\t$absAvg\nLastNonLocalAvg:\t$lastNonLocalAvg\nRelAvg:\t\t\t$relAvg\n\n";        
    }    
    
    ###################################################
    ## Return the requested delay of time in seconds
    ## Return 1 if the delay was less then 1 second
    ###################################################     
    if($measure =~ /relative/gi) {
        if($relAvg == 0) {
            print "1\n";
        } else {
            print "$relAvg\n";
        }
    } else {
        if($absAvg == 0) {
            print "1\n";
        } else {        
            print "$absAvg\n";
        }
    }
}
$pop->Close();