mbsync

mbsync - synchronize IMAP4 and Maildir mailboxes

mbsync [options ...] {{channel[:box[{,|\n}...]]|group} ...|-a}

mbsync is a command line application which synchronizes mailboxes; currently Maildir and IMAP4 mailboxes are supported. New messages, message deletions and flag changes can be propagated both ways; the operation set can be selected in a fine-grained manner.
Synchronization is based on unique message identifiers (UIDs), so no identification conflicts can occur (as opposed to some other mail synchronizers). OTOH, mbsync is susceptible to UID validity changes (that should never happen, but see "Compatibility" in the README). Synchronization state is kept in one local text file per mailbox pair; multiple replicas of a mailbox can be maintained.

-c, --config file

Read configuration from file. By default, the configuration is read from ~/.mbsyncrc.

-a, --all

Select all configured channels. Any channel/group specifications on the command line are ignored.

-l, --list

Don’t synchronize anything, but list all mailboxes in the selected channels and exit.

-C[m][s], --create[-master|-slave]

Override any Create options from the config file. See below.

-X[m][s], --expunge[-master|-slave]

Override any Expunge options from the config file. See below.

{-n|-N|-d|-f|-0|-F}, {--new|--renew|--delete|--flags|--noop|--full}

{-L|-H}[n][N][d][f], {--pull|--push}[-new|-renew|-delete|-flags]

Override any Sync options from the config file. See below.

-h, --help

Display a summary of command line options.

-v, --version

Display version information.

-V, --verbose

Enable verbose mode, which displays the IMAP4 network traffic.

-D, --debug

Enable printing debug information.

-q, --quiet

Suppress informational messages. If specified twice, suppress warning messages as well.

The configuration file is mandatory; mbsync will not run without it. Lines starting with a hash mark (#) are comments and are ignored entirely. Configuration items are keywords followed by one or more arguments; arguments containing spaces must be enclosed in double quotes ("). All keywords (including those used as arguments) are case-insensitive. There are a few global options, the rest applies to particular sections. Sections are started by a section keyword and are terminated by an empty line or end of file. Every section defines an object with a an identifier unique within that object class.

There are two basic object classes: Stores and Channels. A Store defines a collection of mailboxes; basically a folder, either local or remote. A Channel connects two Stores, describing the way the two are synchronized.
There are two auxiliary object classes: Accounts and Groups. An Account describes the connection part of remote Stores, so a server connection can be shared between multiple Stores. A Group aggregates multiple Channels to save typing on the command line.

All Stores

These options can be used in all supported Store types.
In this context, the term "remote" describes the second Store within a Channel, and not necessarily a remote server.
The special mailbox INBOX exists in every Store; its physical location in the file system is Store type specific.

Path path

The location of the Store in the (server’s) file system. If this is no absolute path, the reference point is Store type specific. This string is prepended to the mailbox names addressed in this Store, but is not considered part of them; this is important for Patterns in the Channels section. Note that you must append a slash if you want to specify an entire directory. (Default: "")

MaxSize size[k|m][b]

Messages larger than that will not be propagated into this Store. This is useful for weeding out messages with large attachments. K and M can be appended to the size to specify KiBytes resp. MeBytes instead of bytes. B is accepted but superflous. If size is 0, the maximum message size is unlimited. (Default: 0)

MapInbox mailbox

Create a virtual mailbox (relative to Path), which is backed by the INBOX. Makes sense in conjunction with Patterns in the Channels section.

Trash mailbox

Specifies a mailbox (relative to Path) to copy deleted messages to prior to expunging. See INHERENT PROBLEMS below. (Default: none)

TrashNewOnly yes|no

When trashing, copy only not yet propagated messages. This makes sense if the remote Store has a Trash as well (with TrashNewOnly no). (Default: no)

TrashRemoteNew yes|no

When expunging the remote Store, copy not yet propagated messages to this Store’s Trash. When using this, the remote Store does not need an own Trash at all, yet all messages are archived. (Default: no)

Maildir Stores

The reference point for relative Paths is $HOME.

As mbsync needs UIDs, but no standardized UID storage scheme exists for Maildir, mbsync supports two schemes, each with its pros and cons.
The native scheme is stolen from the latest Maildir patches to c-client and is therefore compatible with pine. The UID validity is stored in a file named .uidvalidity; the UIDs are encoded in the file names of the messages.
The alternative scheme is based on the UID mapping used by isync versions 0.8 and 0.9.x. The invariant parts of the file names of the messages are used as keys into a Berkeley database named .isyncuidmap.db, which holds the UID validity as well.
The native scheme is faster, more space efficient, endianess independent and "human readable", but will be disrupted if a message is copied from another mailbox without getting a new file name; this would result in duplicated UIDs sooner or later, which in turn results in a UID validity change, making synchronization fail. The alternative scheme would fail if a MUA changed a message’s file name in a part mbsync considers invariant; this would be interpreted as a message deletion and a new message, resulting in unnecessary traffic.
Mutt is known to work fine with both schemes.
Use mdconvert to convert mailboxes from one scheme to the other.

MaildirStore name

Define the Maildir Store name, opening a section for its parameters.

AltMap yes|no

Use the alternative UID storage scheme for mailboxes in this Store. This does not affect mailboxes that do already have a UID storage scheme; use mdconvert to change it. (Default: no)

Inbox path

The location of the INBOX. This is not relative to Path. (Default: ~/Maildir)

IMAP4 Accounts

IMAPAccount name

Define the IMAP4 Account name, opening a section for its parameters.

Host host

Specify the DNS name or IP address of the IMAP server.

Port port

Specify the TCP port number of the IMAP server. (Default: 143 for IMAP, 993 for IMAPS)

User username

Specify the login name on the IMAP server. (Default: current local user)

Pass password

Specify the password for username on the IMAP server. Note that this option is NOT required. If no password is specified in the configuration file, mbsync will prompt you for it.

Tunnel command

Specify a command to run to establish a connection rather than opening a TCP socket. This allows you to run an IMAP session over an SSH tunnel, for example. This makes most other IMAPAccount options superflous.

RequireCRAM yes|no

If set to yes, mbsync will abort the connection if no CRAM-MD5 authentication is possible. (Default: no)

UseIMAPS yes|no

If set to yes, the default for Port is changed to 993 and mbsync will start SSL negotiation immediately after establishing the connection to the server.
Note that modern servers support SSL on the regular IMAP port 143 via the STARTTLS extension, which will be used automatically by default.

RequireSSL yes|no

mbsync will abort the connection if a TLS/SSL session cannot be established with the IMAP server. (Default: yes)

CertificateFile path

File containing X.509 CA certificates used to verify server identities. This option is mandatory if SSL is used. See SSL CERTIFICATES below.

UseSSLv2 yes|no

Use SSLv2 for communication with the IMAP server over SSL?
Note that this option is deprecated for security reasons. (Default: no)

UseSSLv3 yes|no

Use SSLv3 for communication with the IMAP server over SSL? (Default: no)

UseTLSv1 yes|no

Use TLSv1 for communication with the IMAP server over SSL? (Default: yes)

IMAP Stores

The reference point for relative Paths is whatever the server likes it to be; probably the user’s $HOME or $HOME/Mail on that server. The location of INBOX is up to the server as well and is usually irrelevant.

IMAPStore name

Define the IMAP4 Store name, opening a section for its parameters.

Account account

Specify which IMAP4 Account to use. Instead of defining an Account and referencing it here, it is also possible to specify all the Account options directly in the Store’s section - this makes sense if an Account is used for one Store only anyway.

UseNamespace yes|no

Selects whether the server’s first "personal" NAMESPACE should be prefixed to mailbox names. Disabling this makes sense for some broken IMAP servers. This option is meaningless if a Path was specified. (Default: yes)

Channels

Channel name

Define the Channel name, opening a section for its parameters.

{Master|Slave} :store:[mailbox]

Specify the Master resp. Slave Store to be connected by this Channel. If mailbox is omitted, INBOX is assumed. The mailbox specification can be overridden by Patterns, which in turn can be overridden by a mailbox list in a Channel reference (a Group specification or the command line).

Pattern[s] [!]pattern ...

Instead of synchronizing only one mailbox pair, synchronize all mailboxes that match the pattern(s). The mailbox names are the same on both Master and Slave. Patterns are IMAP4 patterns, i.e., * matches anything and % matches anything up to the next hierarchy delimiter. Prepending ! to a pattern makes it an exclusion. Multiple patterns can be specified (either by supplying multiple arguments or by using Pattern multiple times); later matches take precedence. Example: "Patterns % !Trash"

MaxSize size[k|m][b]

Analogous to the homonymous option in the Stores section, but applies equally to Master and Slave. Note that this actually modifies the Stores, so take care not to provide conflicting settings if you use the Stores in multiple Channels.

MaxMessages count

Sets the maximum number of messages to keep in each Slave mailbox. This is useful for mailboxes where you keep a complete archive on the server, but want to mirror only the last messages (for instance, for mailing lists). The messages that were the first to arrive in the mailbox (independently of the actual date of the message) will be deleted first. Messages that are flagged (marked as important) and recent messages will not be automatically deleted. If count is 0, the maximum number of messages is unlimited (Default: 0).

Sync {None|[Pull] [Push] [New] [ReNew] [Delete] [Flags]|Full}

Select the synchronization operation(s) to perform:
Pull - propagate changes from Master to Slave.
Push - propagate changes from Slave to Master.
New - propagate newly appeared messages.
ReNew - previously refused messages are re-evaluated for propagation. Useful after flagging affected messages in the source Store or enlarging MaxSize in the destination Store.
Delete - propagate message deletions. This applies only to messages that are actually gone, i.e., were expunged. The affected messages in the remote Store are marked as deleted only, i.e., they won’t be really deleted until that Store is expunged.
Flags - propagate flag changes. Note that Deleted/Trashed is a flag as well; this is particularily interesting if you use mutt with the maildir_trash option.
All (--full on the command line) - all of the above. This is the global default.
None (--noop on the command line) - don’t propagate anything. Useful if you want to expunge only.

Pull and Push are direction flags, while New, ReNew, Delete and Flags are type flags. The two flag classes make up a two-dimensional matrix (a table). Its cells are the individual actions to perform. There are two styles of asserting the cells:
In the first style, the flags select entire rows/colums in the matrix. Only the cells which are selected both horizontally and vertically are asserted. Specifying no flags from a class is like specifying all flags from this class. For example, "Sync Pull New Flags" will propagate new messages and flag changes from the Master to the Slave, "Sync New Delete" will propagate message arrivals and deletions both ways, and "Sync Push" will propagate all changes from the Slave to the Master.
In the second style, direction flags are concatenated with type flags; every compound flag immediately asserts a cell in the matrix. In addition to at least one compound flag, the individual flags can be used as well, but as opposed to the first style, they immediately assert all cells in their respective row/column. For example, "Sync PullNew PullDelete Push" will propagate message arrivals and deletions from the Master to the Slave and any changes from the Slave to the Master. Note that it is not allowed to assert a cell in two ways, e.g. "Sync PullNew Pull" and "Sync PullNew Delete Push" induce error messages.

Create {None|Master|Slave|Both}

Automatically create missing mailboxes [on the Master/Slave]. Otherwise print an error message and skip that mailbox pair if a mailbox does not exist. (Global default: None)

Expunge {None|Master|Slave|Both}

Permanently remove all messages [on the Master/Slave] marked for deletion. (Global default: None)

Sync, Create and Expunge can be used outside any section for a global effect. The global settings are overridden by Channel-specific options, which in turn are overridden by command line switches.

SyncState {*|path}

Set the location of this Channel’s synchronization state files. * means that the state should be saved in a file named .mbsyncstate in the Slave mailbox itself; this has the advantage that you needn’t to care for the state file if you delete the mailbox, but it works only with Maildir mailboxes, obviously. Otherwise this is interpreted as a string to prepend to the Slave mailbox name to make up a complete path.
This option can be used outside any section for a global effect. In this case the appended string is made up according to the pattern :master:master-box_:slave:slave-box.
(Global default: ~/.mbsync/).

Groups

Group name [channel[:box[,...]]] ...

Define the Group name, opening a section for its parameters. Note that even though Groups have an own namespace, they will "hide" Channels with the same name on the command line.
One or more Channels can be specified on the same line.
If you supply one or more boxes to a channel, they will be used instead of what is specified in the Channel. The same can be done on the command line, except that there newlines can be used as mailbox name separators as well.

Channel[s] channel[:box[,...]] ...

Add the specified channels to the group. This option can be specified multiple times within a Group.

[to be done]

Changes done after mbsync has retrieved the message list will not be synchronised until the next time mbsync is invoked.

Using Trash on IMAP Stores bears a race condition: messages will be lost if they are marked as deleted after the message list was retrieved but before the mailbox is expunged. There is no risk as long as the IMAP mailbox is not simultaneously accessed by mbsync and another mail client.

~/.mbsyncrc

Default configuration file

~/.mbsync/

Directory containing synchronization state files

mdconvert(1), isync(1), mutt(1), maildir(5)

Up to date information on mbsync can be found at http://isync.sf.net/

Written by Michael R. Elkins <me@mutt.org>,
rewritten and maintained by Oswald Buddenhagen <ossi@users.sf.net>,
contributions by Theodore Y. Ts’o <tytso@mit.edu>.