Cut it into pieces if you hate the regexes:

#!/usr/bin/env perl

use strict;
use warnings;
use Data::Dump;
use feature qw(say);

my $string =
q(Nov 19 06:37:45 proxy postgrey[2439]: action=pass, reason=triplet fo
+und, client_name=uspmta194080.emarsys.net, client_address=217.175.194
+.80, sender=suite17@xpressus.emarsys.net, recipient=other.one@some.do
+main);

my @fields =
  split /action=|reason=|client_name=|client_address=|sender=|recipien
+t=/,
  $string;

my $date = ( split / proxy.+/, ( shift @fields ) )[0];

say $date;

for ( 0 .. scalar @fields - 1 ) {
    $fields[$_] =~ s/, //;
    say $fields[$_];
}

__END__

karls-mac-mini:monks karl$ ./split.pl
Nov 19 06:37:45
pass
triplet found
uspmta194080.emarsys.net
217.175.194.80
suite17@xpressus.emarsys.net
other.one@some.domain
[download]

I'll burn for this.

Best regards, Karl