I. OfflineIMAP Manual

Table of Contents
offlineimap -- Powerful IMAP/Maildir synchronization and reader support



OfflineIMAP -- Powerful IMAP/Maildir synchronization and reader support


offlineimap [-1] [-P profiledir] [-a accountlist] [-c configfile] [-d debugtype[,...]] [-f foldername[,...]] [-k [section:]option=value] [-l filename] [-o] [-u interface]

offlineimap -h | --help


OfflineIMAP is a tool to simplify your e-mail reading. With OfflineIMAP, you can read the same mailbox from multiple 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 provide 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 features are supported to ensure compatibility with the widest variety of IMAP servers.

OfflineIMAP is SAFE; it uses an algorithm designed to prevent 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. Of course, legally speaking, OfflineIMAP comes with no warranty, so I am not responsible if this turns out to be wrong.

Method of Operation

OfflineIMAP traditionally 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 computer and bi-directionally synchronize them, copying, marking, and deleting messages as necessary.

With OfflineIMAP 4.0, a powerful new ability has been introduced -- the program can now synchronize two IMAP servers with each other, with no need to have a Maildir layer in-between. Many people use this if they use a mail reader on their local machine that does not support Maildirs. People may install an IMAP server on their local machine, and point both OfflineIMAP and their mail reader of choice at it. This is often preferable to the mail reader's own IMAP support since OfflineIMAP supports many features (offline reading, for one) that most IMAP-aware readers don't. However, this feature is not as time-tested as traditional syncing, so my advice is to stick with normal methods of operation for the time being.

Quick Start

If you have already installed OfflineIMAP system-wide, or your system administrator has done that for you, your task for setting up OfflineIMAP for the first time is quite simple. You just need to set up your configuration file, make your folder directory, and run it!

You can quickly set up your configuration file. The distribution includes a file offlineimap.conf.minimal (Debian users may find this at /usr/share/doc/offlineimap/examples/offlineimap.conf.minimal) that is a basic example of setting of OfflineIMAP. You can simply copy this file into your home directory and name it .offlineimaprc (note the leading period). A command such as cp offlineimap.conf.minimal ~/.offlineimaprc will do it. Or, if you prefer, you can just copy this text to ~/.offlineimaprc:

accounts = Test

[Account Test]
localrepository = Local
remoterepository = Remote

[Repository Local]
type = Maildir
localfolders = ~/Test

[Repository Remote]
type = IMAP
remotehost = examplehost
remoteuser = jgoerzen

Now, edit the ~/.offlineimaprc file with your favorite editor. All you have to do is specify a directory for your folders to be in (on the localfolders line), the host name of your IMAP server (on the remotehost line), and your login name on the remote (on the remoteuser line). That's it!

To run OfflineIMAP, you just have to say offlineimap -- it will fire up, ask you for a login password if necessary, synchronize your folders, and exit. See? You can just throw away the rest of this finely-crafted, perfectly-honed manual! Of course, if you want to see how you can make OfflineIMAP FIVE TIMES FASTER FOR JUST $19.95 (err, well, $0), you have to read on!


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 installation with other systems, and a single-user installation. You can download the latest version of OfflineIMAP from the OfflineIMAP website.


In order to use OfflineIMAP, you need to have these conditions satisfied:

  • Your mail server must support IMAP. Most Internet Service Providers and corporate networks do, and most operating systems have an IMAP implementation readily available. A special Gmail mailbox type is available to interface with Gmail's IMAP front-end.

  • You must have Python version 2.4 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 the Python website. If you intend to use the SSL interface, your Python must have been built with SSL support.

  • Have a mail reader that supports the Maildir mailbox 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 compatible with it will work with OfflineIMAP. If you do not have a mail reader that supports Maildir, you can often install a local IMAP server and point both OfflineIMAP and your mail reader at it.

System-Wide Installation, Debian

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, skip to Configuration below. You will type offlineimap to invoke the program.

System-Wide Installation, Other

Download the tar.gz version of the package from the website. Then run these commands, making sure that you are the "root" user first:

tar -zxvf offlineimap_x.y.z.tar.gz
cd offlineimap-x.y.z
python2.2 setup.py install

On some systems, you will need to use python instead of python2.2. Next, proceed to Configuration below. You will type offlineimap to invoke the program.

Single-Account Installation

Download the tar.gz version of the package from the website. 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.py; there is no installation step necessary.


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.

OfflineIMAP also ships a file named offlineimap.conf.minimal that you can also try. It's useful if you want to get started with the most basic feature set, and you can read about other features later with offlineimap.conf.


Most configuration is done via the configuration file. Nevertheless, there are a few command-line options that you may set for OfflineIMAP.


Disable most multithreading operations and use solely a single-connection sync. This effectively sets the maxsyncaccounts and all maxconnections configuration file variables to 1.

-P profiledir

Sets OfflineIMAP into profile mode. The program will create profiledir (it must not already exist). As it runs, Python profiling information about each thread is logged into profiledir. Please note: This option is present for debugging and optimization only, and should NOT be used unless you have a specific reason to do so. It will significantly slow program performance, may reduce reliability, and can generate huge amounts of data. You must use the -1 option when you use -P.

-a accountlist

Overrides the accounts option in the general section of the configuration file. You might use this to exclude certain accounts, or to sync some accounts that you normally prefer not to. Separate the accounts by commas, and use no embedded spaces.

-c configfile

Specifies a configuration file to use in lieu of the default, ~/.offlineimaprc.

-d debugtype[,...]

Enables debugging for OfflineIMAP. 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 to make the results more sensible.

-d requires one or more debugtypes, separated by commas. These define what exactly will be debugged, and include three options: imap, maildir, and thread. The imap option will enable IMAP protocol stream and parsing debugging. Note that the output may contain passwords, so take care to remove that from the debugging output before sending it to anyone else. The maildir option will enable debugging for certain Maildir operations. And thread will debug the threading model.

-f foldername[,foldername]

Only sync the specified folders. The foldernames are the untranslated foldernames. This command-line option overrides any folderfilter and folderincludes options in the configuration file.

-k [section:]option=value

Override configuration file option. If "section" is omitted, it defaults to general. Any underscores "_" in the section name are replaced with spaces: for instance, to override option autorefresh in the "[Account Personal]" section in the config file one would use "-k Account_Personal:autorefresh=30". You may give more than one -k on the command line if you wish.

-l filename

Enables logging to filename. This will log everything that goes to the screen to the specified file. Additionally, if any debugging is specified with -d, then debug messages will not go to the screen, but instead to the logfile only.


Run only once, ignoring all autorefresh settings in the configuration file.


Run only quick synchronizations. Ignore any flag updates on IMAP servers.

-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 pre-defined options are listed in the User Interfaces section.

User Interfaces

OfflineIMAP has a pluggable user interface system that lets you choose how the program communicates information to you. There are two graphical interfaces, two terminal interfaces, and two noninteractive interfaces suitable for scripting or logging purposes. The ui option in the configuration file specifies user interface preferences. The -u command-line option can override the configuration file setting. The available values for the configuration file or command-line are described in this section.


Curses.Blinkenlights is an interface designed to be sleek, fun to watch, and informative of the overall picture of what OfflineIMAP is doing. I consider it to be the best general-purpose interface in OfflineIMAP.

Curses.Blinkenlights contains a row of "LEDs" with command buttons and a log. The log shows more detail about what is happening and is color-coded to match the color of the lights.

Each light in the Blinkenlights interface represents a thread of execution -- that is, a particular task that OfflineIMAP is performing right now. The colors indicate what task the particular thread is performing, and are as follows:


indicates that this light's thread has terminated; it will light up again later when new threads start up. So, black indicates no activity.

Red (Meaning 1)

is the color of the main program's thread, which basically does nothing but monitor the others. It might remind you of HAL 9000 in [2001].


indicates that the thread is establishing a new connection to the IMAP server.


is the color of an account synchronization thread that is monitoring the progress of the folders in that account (not generating any I/O).


indicates that the thread is syncing a folder.


means that a folder's message list is being loaded.


is the color of a message synchronization controller thread.


indicates that an actual message is being copied. (We use fuchsia for fake messages.)

Red (meaning 2)

indicates that a message is being deleted.

Yellow / bright orange

indicates that message flags are being added.

Pink / bright red

indicates that message flags are being removed.

Red / Black Flashing

corresponds to the countdown timer that runs between synchronizations.

The name of this interfaces derives from a bit of computer history. Eric Raymond's [Jargon File] defines blinkenlights, in part, as:

Front-panel diagnostic lights on a computer, esp. a dinosaur. Now that dinosaurs are rare, this term usually refers to status lights on a modem, network hub, or the like.

This term derives from the last word of the famous blackletter-Gothic sign in mangled pseudo-German that once graced about half the computer rooms in the English-speaking world. One version ran in its entirety as follows:


Das computermachine ist nicht fuer gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitzensparken. Ist nicht fuer gewerken bei das dumpkopfen. Das rubbernecken sichtseeren keepen das cotten-pickenen hans in das pockets muss; relaxen und watchen das blinkenlichten.


TTY.TTYUI interface is for people running in basic, non-color terminals. It prints out basic status messages and is generally friendly to use on a console or xterm.


Noninteractive.Basic is designed for situations in which OfflineIMAP will be run non-attended and the status of its execution will be logged. You might use it, for instance, to have the system run automatically and e-mail you the results of the synchronization. This user interface is not capable of reading a password from the keyboard; account passwords must be specified using one of the configuration file options.


Noninteractive.Quiet is designed for non-attended running in situations where normal status messages are not desired. It will output nothing except errors and serious warnings. Like Noninteractive.Basic, this user interface is not capable of reading a password from the keyboard; account passwords must be specified using one of the configuration file options.


Machine.MachineUI generates output in a machine-parsable format. It is designed for other programs that will interface to OfflineIMAP.


Here are some example configurations for various situations. Please e-mail any other examples you have that may be useful to me.

Multiple Accounts with Mutt

This example shows you how to set up OfflineIMAP to synchronize multiple accounts with the mutt mail reader.

Start by creating a directory to hold your folders by running mkdir ~/Mail. Then, in your ~/.offlineimaprc, specify:

accounts = Personal, Work

Make sure that you have both an [Account Personal] and an [Account Work] section. The local repository for each account must have different localfolder path names. Also, make sure to enable [mbnames].

In each local repository section, write something like this:

localfolders = ~/Mail/Personal

Finally, 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

That's it!

UW-IMAPD and References

Some users with a UW-IMAPD server need to use OfflineIMAP's "reference" feature to get at their mailboxes, specifying a reference of "~/Mail" or "#mh/" depending on the configuration. The below configuration from (originally from docwhat@gerf.org) shows using a reference of Mail, a nametrans that strips the leading Mail/ off incoming folder names, and a folderfilter that limits the folders synced to just three.

[Account Gerf]
localrepository = GerfLocal
remoterepository = GerfRemote

[Repository GerfLocal]
type = Maildir
localfolders = ~/Mail

[Repository GerfRemote]
type = IMAP
remotehost = gerf.org
ssl = yes
remoteuser = docwhat
reference = Mail
# Trims off the preceeding Mail on all the folder names.
nametrans = lambda foldername: \
            re.sub('^Mail/', '', foldername)
# Yeah, you have to mention the Mail dir, even though it
# would seem intuitive that reference would trim it.
folderfilter = lambda foldername: foldername in [
maxconnections = 1
holdconnectionopen = no

pythonfile Configuration File Option

You can have OfflineIMAP load up a Python file before evaluating the configuration file options that are Python expressions. This example is based on one supplied by Tommi Virtanen for this feature.

In ~/.offlineimaprc, he adds these options:

[Repository foo]

Then, the ~/.offlineimap.py file will contain:

prioritized = ['INBOX', 'personal', 'announce', 'list']

def mycmp(x, y):
   for prefix in prioritized:
       xsw = x.startswith(prefix)
       ysw = y.startswith(prefix)
       if xsw and ysw:
          return cmp(x, y)
       elif xsw:
          return -1
       elif ysw:
          return +1
   return cmp(x, y)

def test_mycmp():
   import os, os.path
   print folders

This code snippet illustrates how the foldersort option can be customized with a Python function from the pythonfile to always synchronize certain folders first.


OfflineIMAP writes its current PID into ~/.offlineimap/pid when it is running. It is not guaranteed that this file will not exist when OfflineIMAP is not running.


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 particular 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. Usually 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 -r ~/.offlineimap/Account-AccountName/LocalStatus/INBOX
rm -r ~/.offlineimap/Repository-RemoteRepositoryName/FolderValidity/INBOX

(Of course, replace AccountName and RemoteRepositoryName with the names as specified in ~/.offlineimaprc).

Next time you run OfflineIMAP, it will re-download the folder with the new UIDs. Note that the procedure specified above will lose any local changes made to the folder.

Some IMAP servers are broken and do not support UIDs properly. 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.)

This question comes up frequently on the OfflineIMAP mailing list. You can find a detailed discussion of the problem there.

Conforming To


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 propagated to your local copy, and vise-versa. Some people 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 status 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.)

Multiple Instances

OfflineIMAP is not designed to have several instances (for instance, a cron job and an interactive invocation) run over the same mailbox simultaneously. It will perform a check on startup and abort if another OfflineIMAP is already running. If you need to schedule synchronizations, you'll probably find autorefresh settings more convenient than cron. Alternatively, you can set a separate metadata directory for each instance.

Copying Messages Between Folders

Normally, when you copy a message between folders or add a new message to a folder locally, OfflineIMAP will just do the right thing. However, sometimes this can be tricky -- if your IMAP server does not provide the SEARCH command, or does not return something useful, OfflineIMAP cannot determine the new UID of the message. So, in these rare instances, OfflineIMAP will upload the message to the IMAP server and delete it from your local folder. Then, on your next sync, the message will be re-downloaded with the proper UID. OfflineIMAP makes sure that the message was properly uploaded before deleting it, so there should be no risk of data loss.

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. Archives are available at http://lists.complete.org/offlineimap@complete.org/.


Reports of bugs should be reported online at the OfflineIMAP homepage. Debian users are encouraged to instead use the Debian bug-tracking system.

Upgrading to 4.0

If you are upgrading from a version of OfflineIMAP prior to 3.99.12, you will find that you will get errors when OfflineIMAP starts up (relating to ConfigParser or AccountHashGenerator) and the configuration file. This is because the config file format had to change to accommodate new features in 4.0. Fortunately, it's not difficult to adjust it to suit.

First thing you need to do is stop any running OfflineIMAP instance, making sure first that it's synced all your mail. Then, modify your ~/.offlineimaprc file. You'll need to split up each account section (make sure that it now starts with "Account ") into two Repository sections (one for the local side and another for the remote side.) See the files offlineimap.conf.minimal and offlineimap.conf in the distribution if you need more assistance.

OfflineIMAP's status directory area has also changed. Therefore, you should delete everything in ~/.offlineimap as well as your local mail folders.

When you start up OfflineIMAP 4.0, it will re-download all your mail from the server and then you can continue using it like normal.


OfflineIMAP, and this manual, are Copyright © 2002 - 2006 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 the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

imaplib.py comes from the Python dev tree and is licensed under the GPL-compatible PSF license as stated in the file COPYRIGHT in the OfflineIMAP distribution.


OfflineIMAP, its libraries, documentation, and all included files, except where noted, was written by John Goerzen and copyright is held as stated in the COPYRIGHT section.

OfflineIMAP may be downloaded, and information found, from its homepage.

See Also

mutt(1), python(1)


Detailed history may be found in the file ChangeLog in the OfflineIMAP distribution. Feature and bug histories may be found in the file debian/changelog which, despite its name, is not really Debian-specific. This section provides a large overview.

Development on OfflineIMAP began on June 18, 2002. Version 1.0.0 was released three days later on June 21, 2002. Point releases followed, including speed optimizations and some compatibility fixes.

Version 2.0.0 was released on July 3, 2002, and represented the first time the synchronization became multithreaded and, to the best of my knowledge, the first multithreaded IMAP syncrhonizing application in existance. The last 2.0.x release, 2.0.8, was made on July 9.

Version 3.0.0 was released on July 11, 2002, and introduced modular user interfaces and the first GUI interface for OfflineIMAP. This manual also was introduced with 3.0.0, along with many command-line options. Version 3.1.0 was released on July 21, adding the Noninteractive user interfaces, profiling support, and several bugfixes. 3.2.0 was released on July 24, adding support for the Blinkenlights GUI interface. OfflineIMAP entered maintenance mode for awhile, as it had reached a feature-complete milestone in my mind.

The 3.99.x branch began in on October 7, 2002, to begin work for 4.0. The Curses.Blinkenlights interface was added in 3.99.6, and many architectural changes were made.

4.0.0 was released on July 18, 2003, including the ability to synchronize directly between two IMAP servers, the first re-architecting of the configuration file to refine the notion of an account, and the new Curses interface.