mailutils-2.1-alt0.20090928.3

I tried to mainatin a local (backup) copy of a remote IMAP mailbox with "movemail": obviously, I wanted that the second and furhther calls to "movemail" only transfer the new and updated messages, but in reality, "movemail" creates second copies of the already downloaded messages.

"movemail" has an option with a semantics close to what I want; from "info mailutils": 

2.6.1 Movemail Configuration
----------------------------
....
 -- Movemail Config: uidl BOOL
     Avoid copying the message if a message with the same UIDL already
     exists in the destination mailbox.

And some general info about "UIDL" from http://en.wikipedia.org/wiki/UIDL#Overview :

Clients with a leave mail on server option generally use the POP3 UIDL (Unique IDentification Listing) command. Most POP3 commands identify specific messages by their ordinal number on the mail server. <...> UIDL provides a mechanism to avoid these numbering issues by assigning a string of characters as a permanent and unique ID for the message. <...> IMAP uses a 32-bit unique identifier (UID) that is assigned to messages in ascending (although not necessarily consecutive) order as they are received. When retrieving new messages, an IMAP client requests the UIDs greater than the highest UID among all previously-retrieved messages, whereas a POP client must fetch the entire UIDL map. For large mailboxes, this can require significant processing.

So, in principle, a mechanism analoguous to UIDL is present in IMAP, and is even more effecient than its POP counterpart, so "movemail" could use it to download only new messages.

But in practice, this is not so.

A test case (the user "z" is a user for tests, the computer "arrakis" is running uw-imap-2001a-alt9.1):

[ivan@dell ~]$ ssh arrakis 
Last login: Sat Nov  7 10:50:06 2009 from dell.zephyrous
[ivan@arrakis data]$ sudo rm /var/mail/z
[ivan@arrakis data]$ sudo touch /var/mail/z
[ivan@arrakis data]$ sudo chown z /var/mail/z
[ivan@arrakis data]$ l /var/mail/z
-rw-r--r--  1 z mail 0 Ноя  7 11:29 /var/mail/z
[ivan@arrakis data]$ mail z
Subject: test message A
test
Cc: 
[ivan@arrakis data]$ exit
Connection to arrakis closed.
[ivan@dell ~]$ movemail --verbose --keep --uidl 'imap://z@arrakis/INBOX' 'maildir:/home/ivan/tmp/z-mail-INBOX'
Imap Passwd: 
movemail: info: number of messages in source mailbox: 1
movemail: info: number of processed messages: 1
[ivan@dell ~]$ l -R tmp/z-mail-INBOX/
tmp/z-mail-INBOX/:
total 16
drwx------   5 ivan ivan   144 Ноя  7 11:38 ./
drwxrwx--T 360 root ivan 12248 Ноя  7 11:38 ../
drwx------   2 ivan ivan    48 Ноя  7 11:38 cur/
-rw-r--r--   1 ivan ivan     3 Ноя  7 11:38 .mu-size
drwx------   2 ivan ivan   104 Ноя  7 11:38 new/
drwx------   2 ivan ivan    48 Ноя  7 11:38 tmp/

tmp/z-mail-INBOX/cur:
total 0
drwx------ 2 ivan ivan  48 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../

tmp/z-mail-INBOX/new:
total 4
drwx------ 2 ivan ivan 104 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
-rw------- 1 ivan ivan 561 Ноя  7 11:38 1257583083.M183312P16581Q0.dell.humboldt

tmp/z-mail-INBOX/tmp:
total 0
drwx------ 2 ivan ivan  48 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
[ivan@dell ~]$ movemail --verbose --keep --uidl 'imap://z@arrakis/INBOX' 'maildir:/home/ivan/tmp/z-mail-INBOX'
Imap Passwd: 
movemail: info: number of messages in source mailbox: 1
movemail: info: number of processed messages: 1
[ivan@dell ~]$ l -R tmp/z-mail-INBOX/
tmp/z-mail-INBOX/:
total 16
drwx------   5 ivan ivan   144 Ноя  7 11:38 ./
drwx------   2 ivan ivan   112 Ноя  7 11:38 cur/
-rw-r--r--   1 ivan ivan     4 Ноя  7 11:38 .mu-size
drwx------   2 ivan ivan   104 Ноя  7 11:38 new/
drwx------   2 ivan ivan    48 Ноя  7 11:38 tmp/
drwxrwx--T 360 root ivan 12248 Ноя  7 11:38 ../

tmp/z-mail-INBOX/cur:
total 4
drwx------ 2 ivan ivan 112 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
-rw------- 1 ivan ivan 561 Ноя  7 11:38 1257583083.M183312P16581Q0.dell.humboldt:2

tmp/z-mail-INBOX/new:
total 4
drwx------ 2 ivan ivan 104 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
-rw------- 1 ivan ivan 545 Ноя  7 11:38 1257583105.M518684P16583Q1.dell.humboldt

tmp/z-mail-INBOX/tmp:
total 0
drwx------ 2 ivan ivan  48 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
[ivan@dell ~]$ movemail --verbose --keep --uidl 'imap://z@arrakis/INBOX' 'maildir:/home/ivan/tmp/z-mail-INBOX'
Imap Passwd: 
movemail: info: number of messages in source mailbox: 1
movemail: info: number of processed messages: 1
[ivan@dell ~]$ l -R tmp/z-mail-INBOX/
tmp/z-mail-INBOX/:
total 16
drwx------   5 ivan ivan   144 Ноя  7 11:38 ./
drwx------   2 ivan ivan   176 Ноя  7 11:38 cur/
-rw-r--r--   1 ivan ivan     4 Ноя  7 11:38 .mu-size
drwx------   2 ivan ivan   104 Ноя  7 11:38 new/
drwx------   2 ivan ivan    48 Ноя  7 11:38 tmp/
drwxrwx--T 360 root ivan 12248 Ноя  7 11:38 ../

tmp/z-mail-INBOX/cur:
total 8
drwx------ 2 ivan ivan 176 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
-rw------- 1 ivan ivan 561 Ноя  7 11:38 1257583083.M183312P16581Q0.dell.humboldt:2
-rw------- 1 ivan ivan 545 Ноя  7 11:38 1257583105.M518684P16583Q1.dell.humboldt:2

tmp/z-mail-INBOX/new:
total 4
drwx------ 2 ivan ivan 104 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
-rw------- 1 ivan ivan 545 Ноя  7 11:38 1257583111.M478896P16585Q2.dell.humboldt

tmp/z-mail-INBOX/tmp:
total 0
drwx------ 2 ivan ivan  48 Ноя  7 11:38 ./
drwx------ 5 ivan ivan 144 Ноя  7 11:38 ../
[ivan@dell ~]$ 

So, the number of the copies of the message is growing.

(Possible alternative solutions/tools for this task one could try: 

* "mailutil" from uw-imap or pine or alpiane -- http://www.washington.edu/imap/ ;

* http://freshmeat.net/projects/imapsync ;

* http://blog.hoopycat.com/2009/07/imap2maildir-a-tool-for-mirroring-imap-t , http://github.com/rtucker/imap2maildir ;

* http://en.wikipedia.org/wiki/Getmail ;

* fetchmail.
)