Transferring Mails to a New Server

What happens when your current mail server is not meeting your demand? You have to get something new to top the performance. Of course if it is as easy as everyone using POP, then we do not need to fret over it since with POP, you can just shut off the incoming mail port and wait long enough for everyone to download their share of mails and the server is empty. In most cases, it isn’t the case.

Nowadays, users tend to use IMAP. IMAP protocol keeps a copy of the emails in the server. Many users let their mailboxes build up without ever deleting unneeded messages. If you can leave the old server on the network, they can always access their old mail if they need to, but you may find after a year or so that nobody ever access it. You might then archive the messages "Just in case" and take down the old server.

If you do want to transfer messages, it can be as simple as running command line tools. The first thing to do is to set the old server to forward all mail to the new server. Exactly what you do to accomplish that depends on your server, but it should be easy. For sendmail, you'd set SMART_HOST and MAIL_HUB, or edit the aliases file and forward each user. For SME server, set the "Delegate Mail Server" in the Server Manager.

Transferring existing mail depends on the format it now uses. For example, Qmail stores messages in individual files. On an SME server (which uses Qmail) you could transfer "tony"'s current mail with just this:

cd /home/e-smith/files/users/tony/Maildir

for i in *

do 

 cat $i | /var/qmail/bin/qmail-inject

done

Repeating that for each directory would move all mail to the new server. However, it all ends up in the user's INBOX unless that server can apply rules to determine where to file it. To assist that, you may want to use a Perl program instead. Something as the one below:

#!/usr/bin/perl

use Mail::Mailer;

@stuff=<>;

foreach (@stuff) {

    $from=$_ if /^From:/;

    $to=$_ if /^To:/;

    $subject=$_ if /^Subject:/;

    last if $subject;

}

$from=~ s/From: //;

$from=~ s/<//;

$from=~ s/>//;

$to=~ s/To: //;

$to=~ s/<//;

$to=~ s/>//;

$subject=~ s/^/*** FILE ME IN CUSTS ***/;

$mailer=Mail::Mailer->new();

$mailer->open({From =>$from,

               To => $to,

               Subject => $subject,

           }) or die "Can't open $!n";

foreach (@stuff) {

    print $mailer $_;

}

$mailer=>close();

You'd adjust the modification to Subject appropriately, or add entirely new headers if desired.

If your mail is stored in UNIX mailbox fashion, you need something to read the messages and break them up. While you could read the mailboxes directly, it's more portable to use tools like POP:

#!/usr/bin/perl

use Net::POP3;

$pop=Net::POP3->new('10.1.36.237') or die "$!";

$pop->login("tony","password");

$messages=$pop->list;

foreach $msg(keys %$messages) {

  $message=$pop->get($msg);

  foreach (@$message) {

    #same basic idea as above, 

  }

}

You may need to get Net::POP3 from CPAN. There are similar modules for IMAP.