I'm having difficulty getting this code of Discipulus' to work--actually, I think his code is fine and wonder about my dovecot instance--and have stripped things down to a test case:

#!/usr/bin/perl

use strict;
use warnings;
use Mail::IMAPClient;

my $now = time;
print "Now is $now\n";
(my $username, my $password) = ('re','dacted');
my $imap = Mail::IMAPClient->new(Server => 'localhost', 
                                             User => $username,
                                             Password => $password,
                                             Port => '143');
die "failed to instantiate $@." unless defined $imap;

my $select = $imap->select('INBOX');
my @messages = $imap->messages('INBOX');
print "All @messages\n";

sleep 15; #<---Here's where I generate fresh mail, during the sleep
$select = $imap->select('INBOX');
@messages = $imap->sentsince($now);
print "Some @messages\n";
print "Now then was $now\n";
$now = time;
print "Now now is $now\n";
[download]

Which gives me these results:

Now is 1752071233
All 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3
+456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469
Some 
Now then was 1752071233
Now now is 1752071248
[download]

What I expect is for the new mail to show up in the Some line, but it does not.