Read/sync your IMAP mailboxes [Python]
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1.1   Description

Welcome to the official OfflineIMAP project.

NOTICE: this software was written by John Goerzen, who retired from maintaining. It is now maintained by Nicolas Sebrecht at Thanks to John for his great job and to have share this project with us.

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 works on pretty much any POSIX operating system, such as Linux, BSD operating systems, MacOS X, Solaris, etc.

OfflineIMAP is a Free Software project licensed under the GNU General Public License. You can download it for free, and you can modify it. In fact, you are encouraged to contribute to OfflineIMAP, and doing so is fast and easy.

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.

1.2   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.

1.3   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!

1.4   Documentation

If you are reading this file on github, you can find more documentations in the docs directory.

Using your git repository, you can generate documentation with:

$ make doc

1.5   Mailing list

The user discussion, development and all exciting stuff take place in the mailing list. You're NOT supposed to subscribe to send emails.

1.6   Reporting bugs and contributions

1.6.1   Bugs

Bugs, issues and contributions should be reported to the mailing list. Please, don't use the github features (messages, pull requests, etc) at all. It would most likely be discarded or ignored.

2   Examples

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

2.1   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=""
folder-hook Work set from=""
set mbox_type=Maildir
set folder=$HOME/Mail

That's it!

2.2   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 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 =
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

2.3   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 ~/ 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.

2.4   Signals

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.

<!-- not done yet

You can send SIGINT to OfflineIMAP using this file to kill it. SIGUSR1 will force an immediate resync of all accounts. This will be ignored for all accounts for which a resync is already in progress.