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OFFLINEIMAP(1) OfflineIMAP manual OFFLINEIMAP(1)
NAME
OfflineIMAP - Powerful IMAP/Maildir synchronization and
reader support
SYNOPSIS
offlineimap [ -1 ] [ -a accountlist ] [ -c configfile ]
[ -d ] [ -u interface ]
offlineimap -h | --help
DESCRIPTION
OfflineIMAP is a tool to simplify your e-mail reading.
With OfflineIMAP, you can read the same mailbox from mul-
tiple computers. You get a current copy of your messages
on each computer, and changes you make one place will be
visible on all other systems. For instance, you can
delete a message on your home computer, and it will appear
deleted on your work computer as well. OfflineIMAP is
also useful if you want to use a mail reader that does not
have IMAP support, has poor IMAP support, or does not pro-
vide disconnected operation.
OfflineIMAP is FAST; it synchronizes my two accounts with
over 50 folders in 3 seconds. Other similar tools might
take over a minute, and achieve a less-reliable result.
Some mail readers can take over 10 minutes to do the same
thing, and some don't even support it at all. Unlike
other mail tools, OfflineIMAP features a multi-threaded
synchronization algorithm that can dramatically speed up
performance in many situations by synchronizing several
different things simultaneously.
OfflineIMAP is FLEXIBLE; you can customize which folders
are synced via regular expressions, lists, or Python
expressions; a versatile and comprehensive configuration
file is used to control behavior; two user interfaces are
built-in; fine-tuning of synchronization performance is
possible; internal or external automation is supported;
SSL and PREAUTH tunnels are both supported; offline (or
"unplugged") reading is supported; and esoteric IMAP fea-
tures are supported to ensure compatibility with the
widest variety of IMAP servers.
OfflineIMAP is SAFE; it uses an algorithm designed to pre-
vent mail loss at all costs. Because of the design of
this algorithm, even programming errors should not result
in loss of mail. I am so confident in the algorithm that
I use my own personal and work accounts for testing of
OfflineIMAP pre-release, development, and beta releases.
METHOD OF OPERATION
OfflineIMAP operates by maintaining a hierarchy of mail
folders in Maildir format locally. Your own mail reader
will read mail from this tree, and need never know that
the mail comes from IMAP. OfflineIMAP will detect changes
to the mail folders on your IMAP server and your own com-
puter and bi-directionally synchronize them, copying,
marking, and deleting messages as necessary.
INSTALLATION
If you are reading this document via the "man" command, it
is likely that you have no installation tasks to perform;
your system administrator has already installed it. If
you need to install it yourself, you have three options: a
system-wide installation with Debian, system-wide instal-
lation with other systems, and a single-user installation.
You can download the latest version of OfflineIMAP from
http://quux.org/devel/offlineimap/.
PREREQUISITES
In order to use OfflineIMAP, you need to have these condi-
tions satisfied:
o Your mail server must support IMAP. Most Internet
Service Providers and corporate networks do, and
most operating systems have an IMAP implementation
readily available.
o You must have Python version 2.2.1 or above
installed. If you are running on Debian GNU/Linux,
this requirement will automatically be taken care
of for you. If you do not have Python already,
check with your system administrator or operating
system vendor; or, download it from
http://www.python.org/. If you intend to use the
Tk interface, you must have Tkiner (python-tk)
installed. If you intend to use the SSL interface,
your Python must have been built with SSL support.
o Have a mail reader that supports the Maildir mail-
box format. Most modern mail readers have this
support built-in, so you can choose from a wide
variety of mail servers. This format is also known
as the "qmail" format, so any mail reader compati-
ble with it will work with OfflineIMAP.
DEBIAN SYSTEM-WIDE INSTALLATION
If you are tracking Debian unstable, you may install
OfflineIMAP by simply running the following command as
root:
apt-get install offlineimap
If you are not tracking Debian unstable, download the
Debian .deb package from the OfflineIMAP website and then
run dpkg -i to install the downloaded package. Then, go
to CONFIGURATION below. You will type offlineimap to
invoke the program.
OTHER SYSTEM-WIDE INSTALLATION
Download the tar.gz version of the package from the web-
site. Then run these commands:
tar -zxvf offlineimap-x.y.z.tar.gz
cd offlineimap-x.y.z
python2.2 setup.py
Some systems will need to use python instead of python2.2.
Next, proceed to configuration. You will type offlineimap
to invoke the program.
SINGLE-ACCOUNT INSTALLATION
Download the tar.gz version of the package from the web-
site. Then run these commands:
tar -zxvf offlineimap-x.y.z.tar.gz
cd offlineimap-x.y.z
When you want to run OfflineIMAP, you will issue the cd
command as above and then type ./offlineimap; there is no
installation step necessary.
CONFIGURATION
OfflineIMAP is regulated by a configuration file that is
normally stored in ~/.offlineimaprc. OfflineIMAP ships
with a file named offlineimap.conf that you should copy to
that location and then edit. This file is vital to proper
operation of the system; it sets everything you need to
run OfflineIMAP. Full documentation for the configuration
file is included within the sample file.
OPTIONS
Most configuration is done via the configuration file.
Nevertheless, there are a few options that you may set for
OfflineIMAP.
-1 Disable all multithreading operations and use
solely a single-thread sync. This effectively sets
the maxsyncaccounts and all maxconnections configu-
ration file variables to 1.
-a accountlist
Overrides the accounts section in the config file.
Lets you specify a particular account or set of
accounts to sync without having to edit the config
file. You might use this to exclude certain
accounts, or to sync some accounts that you nor-
mally prefer not to.
-c configfile
Specifies a configuration file to use in lieu of
the default, ~/.offlineimaprc.
-d Enables IMAP protocol stream and parsing debugging.
This is useful if you are trying to track down a
malfunction or figure out what is going on under
the hood. I suggest that you use this with -1 in
order to make the results more sensible. Note that
this output will contain full IMAP protocol in
plain text, including passwords, so take care to
remove that from the debugging output before send-
ing it to anyone else.
-h, --help
Show summary of options.
-u interface
Specifies an alternative user interface module to
use. This overrides the default specified in the
configuration file. The UI specified with -u will
be forced to be used, even if its isuable() method
states that it cannot be. Use this option with
care.
EXAMPLES
Here is an example configuration for a particularly com-
plex situation; more examples will be added later.
MULTIPLE ACCOUNTS WITH MUTT
This example shows you how to set up OfflineIMAP to syn-
chronize multiple accounts with the mutt mail reader.
Start by creating a directory to hold your folders:
mkdir ~/Mail
In your ~/.offlineimaprc, specify this:
accounts = Personal, Work
Make sure that you have both a [Personal] and a [Work]
section, with different localfolder pathnames and enable
[mbnames].
In each account section, do something like this:
localfolders = ~/Mail/Personal
Add these lines to your ~/.muttrc:
source ~/path-to-mbnames-muttrc-mailboxes
folder-hook Personal set from="youremail@personal.com"
folder-hook Work set from="youremail@work.com"
set mbox_type=Maildir
set folder=$HOME/Mail
set spoolfile=+Personal/INBOX
That's it!
ERRORS
If you get one of some frequently-encountered or confusing
errors, please check this section.
UID validity problem for folder
IMAP servers use a unique ID (UID) to refer to a specific
message. This number is guaranteed to be unique to a par-
ticular message FOREVER. No other message in the same
folder will ever get the same UID. UIDs are an integral
part of OfflineIMAP's synchronization scheme; they are
used to match up messages on your computer to messages on
the server.
Sometimes, the UIDs on the server might get reset. Usu-
ally this will happen if you delete and then recreate a
folder. When you create a folder, the server will often
start the UID back from 1. But OfflineIMAP might still
have the UIDs from the previous folder by the same name
stored. OfflineIMAP will detect this condition and skip
the folder. This is GOOD, because it prevents data loss.
You can fix it by removing your local folder and cache
data. For instance, if your folders are under ~/Folders
and the folder with the problem is INBOX, you'd type this:
rm -r ~/Folders/INBOX
rm ~/.offlineimap/AccountName/INBOX
(replacing AccountName with the account name as specified
in ~/.offlineimaprc)
Next time you run OfflineIMAP, it will re-download the
folder with the new UIDs. Note that the procedure speci-
fied above will lose any local changes made to the folder.
Some IMAP servers are broken and do not support UIDs prop-
erly. If you continue to get this error for all your
folders even after performing the above procedure, it is
likely that your IMAP server falls into this category.
OfflineIMAP is incompatible with such servers. Using
OfflineIMAP with them will not destroy any mail, but at
the same time, it will not actually synchronize it either.
(OfflineIMAP will detect this condition and abort prior to
synchronization)
OTHER FREQUENTLY ASKED QUESTIONS
There are some other FAQs that might not fit into another
section of this document, and they are enumerated here.
What platforms does OfflineIMAP run on?
It should run on most platforms supported by
Python, which are quite a few.
I'm using Mutt. Other IMAP sync programs require me to use
set maildir_trash=yes . Do I need to do that with
OfflineIMAP?
No. OfflineIMAP is smart enough to figure out mes-
sage deletion without this extra crutch. You'll
get the best results if you don't use this setting,
in fact.
How do I specify the names of my folders?
You do not need to. OfflineIMAP is smart enough to
automatically figure out what folders are present
on the IMAP server and synchronize them. You can
use the folderfilter and foldertrans configuration
file options to request certain folders and rename
them as they come in if you like.
How can I prevent certain folders from being synced?
Use the folderfilter option in the configuration
file.
How can I add or delete a folder?
OfflineIMAP does not currently provide this fea-
ture, but if you create a new folder on the IMAP
server, it will be created locally automatically.
Are there any other warnings that I should be aware of?
Yes; see the NOTES section below.
What is the mailbox name recorder (mbnames) for?
The Mutt mail reader is not capable of automati-
cally determining the names of your mailboxes.
OfflineIMAP can help it (or many other) programs
out be writing these names out in a format you
specify. See the example offlineimap.conf file for
details.
Can I synchronize multiple accounts with OfflineIMAP?
Sure. Just name them all in the accounts line in
the general section of the config file, and add a
per-account section for each one.
Does OfflineIMAP support POP?
No. POP is not robust enough to do a completely
reliable multi-machine synchronization like
OfflineIMAP can do. OfflineIMAP will not support
it.
Do you support mailbox formats other than Maildir?
Not at present. There is no technical reason not
to; just no demand yet. Maildir is a superior for-
mat anyway.
[technical] Why are your Maildir message filenames so
huge?
OfflineIMAP has two relevant principles: 1) never
modifying your messages in any way and 2) ensuring
100% reliable synchronizations. In order to do a
reliable sync, OfflineIMAP must have a way to
uniquely identify each e-mail. Three pieces of
information are required to do this: your account
name, the folder name, and the message UID. The
account name can be calculated from the path in
which your messages are. The folder name can usu-
ally be as well, BUT some mail clients move mes-
sages between folders by simply moving the file,
leaving the name intact.
So, OfflineIMAP must store both a UID folder ID.
The folder ID is necessary so OfflineIMAP can
detect a message moved to a different folder.
OfflineIMAP stores the UID (U= number) and an
md5sum of the foldername (FMD5= number) to facili-
tate this.
What is the speed of OfflineIMAP's sync?
OfflineIMAP versions 2.0 and above contain a multi-
threaded system. A good way to experiment is by
setting maxsyncaccounts to 3 and maxconnections to
3 in each account clause.
This lets OfflineIMAP open up multiple connections
simultaneously. That will let it process multiple
folders and messages at once. In most cases, this
will increase performance of the sync.
Don't set the number too high. If you do that,
things might actually slow down as your link gets
saturated. Also, too many connections can cause
mail servers to have excessive load. Administra-
tors might take unkindly to this, and the server
might bog down. There are many variables in the
optimal setting; experimentation may help.
An informal benchmark yields these results for my
setup:
10 minutes with MacOS X Mail.app "manual cache"
5 minutes with GNUS agent sync
20 seconds with OfflineIMAP 1.x
9 seconds with OfflineIMAP 2.x
3 seconds with OfflineIMAP 3.x "cold start"
2 seconds with OfflineIMAP 3.x "held connection"
CONFORMING TO
o Internet Message Access Protocol version 4rev1
(IMAP 4rev1) as specified in RFC2060
o Maildir as specified in http://www.qmail.org/qmail-
manual-html/man5/maildir.html and
http://cr.yp.to/proto/maildir.html.
o Standard Python 2.2.1 as implemented on POSIX-com-
pliant systems.
NOTES
DELETING LOCAL FOLDERS
OfflineIMAP does a two-way synchronization. That is, if
you make a change to the mail on the server, it will be
propogated to your local copy, and vise-versa. Some peo-
ple might think that it would be wise to just delete all
their local mail folders periodically. If you do this
with OfflineIMAP, remember to also remove your local sta-
tus cache (~/.offlineimap by default). Otherwise,
OfflineIMAP will take this as an intentional deletion of
many messages and will interpret your action as requesting
them to be deleted from the server as well. (If you don't
understand this, don't worry; you probably won't encounter
this situation)
MAILING LIST
There is an OfflineIMAP mailing list available.
To subscribe, send the text "Subscribe" in the subject of
a mail to offlineimap-request@complete.org. To post, send
the message to offlineimap@complete.org.
BUGS
Should be reported to the author at the address specified
below.
COPYRIGHT
OfflineIMAP is Copyright (C) 2002 John Goerzen.
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 (at your option) 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:
Free Software Foundation, Inc.
59 Temple Place
Suite 330
Boston, MA 02111-1307
USA
AUTHOR
OfflineIMAP, its libraries, documentation, and all
included files, except where noted, was written by John
Goerzen <jgoerzen@complete.org> and copyright is held as
stated in the COPYRIGHT section.
OfflineIMAP may be downloaded, and information found, from
its homepage via either Gopher or HTTP:
gopher://quux.org/1/devel/offlineimap
http://quux.org/devel/offlineimap
SEE ALSO
mutt(1), python(1).
John Goerzen July 11, 2002 OFFLINEIMAP(1)