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.
Read configuration from file.
By default, the configuration is read from ~/.mbsyncrc.
Select all configured channels. Any channel/group specifications on the command
line are ignored.
Don't synchronize anything, but list all mailboxes in the selected channels
Override any Create options from the config file. See below.
Override any Expunge options from the config file. See below.
Override any Sync options from the config file. See below.
Display a summary of command line options.
Display version information.
Enable verbose mode, which displays the IMAP4 network traffic.
Enable printing debug information.
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
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.
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.
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
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.
Create a virtual mailbox (relative to Path), which is backed by
the INBOX. Makes sense in conjunction with Patterns in the
Specifies a mailbox (relative to Path) to copy deleted messages to
prior to expunging. See INHERENT PROBLEMS below.
When trashing, copy only not yet propagated messages. This makes sense if the
remote Store has a Trash as well (with TrashNewOnlyno).
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.
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
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.
Define the Maildir Store name, opening a section for its parameters.
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.
The location of the INBOX. This is not relative to Path.
Define the IMAP4 Account name, opening a section for its parameters.
Specify the DNS name or IP address of the IMAP server.
Specify the TCP port number of the IMAP server. (Default: 143 for IMAP,
993 for IMAPS)
Specify the login name on the IMAP server. (Default: current local user)
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.
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.
If set to yes, mbsync will abort the connection if no CRAM-MD5
authentication is possible. (Default: 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.
mbsync will abort the connection if a TLS/SSL session cannot be
established with the IMAP server. (Default: yes)
File containing X.509 CA certificates used to verify server identities.
This option is mandatory if SSL is used. See SSL CERTIFICATES below.
Use SSLv2 for communication with the IMAP server over SSL?
Note that this option is deprecated for security reasons.
Use SSLv3 for communication with the IMAP server over SSL?
Use TLSv1 for communication with the IMAP server over SSL?
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.
Define the IMAP4 Store name, opening a section for its parameters.
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.
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.
Define the Channel name, opening a section for its parameters.
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"
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.
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
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
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, "SyncPullNewFlags" will propagate
new messages and flag changes from the Master to the Slave,
"SyncNewDelete" will propagate message arrivals and
deletions both ways, and "SyncPush" 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,
"SyncPullNewPullDeletePush" 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.
"SyncPullNewDeletePush" induce error messages.
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)
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.
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
(Global default: ~/.mbsync/).
Groupname [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.