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# isync

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isync is a command line application to synchronize mailboxes; it supports Maildir and IMAP4 mailboxes. New messages, message deletions and flag changes can be propagated both ways.

Synchronization is based on unique message identifiers (UIDs), so no identification conflicts can occur (as opposed to some other mail synchronizers). Synchronization state is kept in one local text file per mailbox pair; multiple replicas of a mailbox can be maintained.

Note: isync is the name of the project, mbsync is the name of the executable

## Installing

Install the isync package.

## Configuring

This article or section is out of date.

Reason: The access to lesssecureapps is no longer possible without two-factor authentication. (Discuss in Talk:Isync)
Note:

- Google appears to block isync from downloading emails by default. If you have 2-step authentication enabled, you need to set up an app password and use that with isync, otherwise you need to go to Google's Security Page and toggle "Allow less secure apps" to "on".
- Subfolders setting in MaildirStore now seems to be required to be set: iSync Config SubFolders SubFolders Legacy worked as previous unset - Oct 2017

First, a main configuration file needs to be created, either as `isyncrc` in the user's `XDG_CONFIG_HOME` directory, or `.mbsyncrc` in the user's home directory root. The package supplies an example `/usr/share/doc/isync/examples/mbsyncrc.sample` file. Another example for a Google-mail account is as follows:

    ~/.mbsyncrc

    IMAPAccount gmail
    # Address to connect to
    Host imap.gmail.com
    User username@gmail.com
    Pass ***************
    # To store the password in an encrypted file use PassCmd instead of Pass
    # PassCmd "gpg2 -q --for-your-eyes-only --no-tty -d ~/.mailpass.gpg"
    #
    # Use TLS
    TLSType IMAPS
    # The following line should work. If you get certificate errors, uncomment the two following lines and read the "Troubleshooting" section.
    CertificateFile /etc/ssl/certs/ca-certificates.crt
    #CertificateFile ~/.cert/imap.gmail.com.pem
    #CertificateFile ~/.cert/Equifax_Secure_CA.pem

    IMAPStore gmail-remote
    Account gmail

    MaildirStore gmail-local
    SubFolders Verbatim
    # The trailing "/" is important
    Path ~/.mail/gmail/
    Inbox ~/.mail/gmail/Inbox

    Channel gmail
    Far :gmail-remote:
    Near :gmail-local:
    # Exclude everything under the internal [Gmail] folder, except the interesting folders
    Patterns * ![Gmail]* "[Gmail]/Sent Mail" "[Gmail]/Starred" "[Gmail]/All Mail"
    # Or include everything
    #Patterns *
    # Automatically create missing mailboxes, both locally and on the server
    Create Both
    # Sync the movement of messages between folders and deletions, add after making sure the sync works
    Expunge Both
    # Save the synchronization state files in the relevant directory
    SyncState *

It is possible to avoid the proprietary `[Gmail]` (or `[Google Mail]`) folder categorization by using separate channels for each directory, and later merging them to a group:

    ~/.mbsyncrc

    Channel sync-googlemail-default
    Far :gmail-remote:
    Near :gmail-local:
    # Select some mailboxes to sync
    Patterns "INBOX" "arch"
    Create Both

    Channel sync-googlemail-sent
    Far :gmail-remote:"[Google Mail]/Gesendet"
    Near :gmail-local:sent
    Create Near

    Channel sync-googlemail-trash
    Far :gmail-remote:"[Google Mail]/Papierkorb"
    Near :gmail-local:trash
    Create Near

    # Get all the channels together into a group.
    Group googlemail
    Channel sync-googlemail-default
    Channel sync-googlemail-sent
    Channel sync-googlemail-trash

As you can see, name-translations are possible this way as well.

## Usage

First make any folders that were specified as Maildirs:

    $ mkdir -p ~/.mail/gmail

Then to retrieve the mail for a specific channel run:

    $ mbsync gmail

or to retrieve the mail for all channels:

    $ mbsync -a

## Tips and tricks

### Using Path and/or Inbox on NTFS partitions

Since NTFS partitions will not accept a semicolon in a filename, you need to change your InfoDelimiter and your FieldDelimiter to something else, you can achieve this by globaly (outside any store or channel configuration) changing the later, like below:

    ~/.mbsyncrc

    FieldDelimiter -

### Importing EML emails

Importing emails in the EML format is achieved by copying the `.eml` files under the `cur` directory of the desired Maildir directory. For example, using `mv message.eml ~/.mail/myaccount/Inbox`. The new emails should be detected during the subsequent run of `mbsync`.

### Calling mbsync automatically

#### With a timer

If you want to automatically synchronize your mailboxes, isync can be started automatically with a systemd/User unit. The following service file can start the `mbsync` command:

    ~/.config/systemd/user/mbsync.service

    [Unit]
    Description=Mailbox synchronization service

    [Service]
    Type=oneshot
    ExecStart=/usr/bin/mbsync -Va

    [Install]
    WantedBy=default.target

The following timer configures `mbsync` to be started 2 minutes after boot, and then every 5 minutes:

    ~/.config/systemd/user/mbsync.timer

    [Unit]
    Description=Mailbox synchronization timer

    [Timer]
    OnBootSec=2m
    OnUnitActiveSec=5m
    Unit=mbsync.service

    [Install]
    WantedBy=timers.target

Once those two files are created, reload systemd, then enable and start `mbsync.timer`, adding the `--user` flag to `systemctl`.

Tip: The mbsync service now only runs after login. It's also possible to launch the systemd-user instances after boot if you configure Systemd/User#Automatic start-up of systemd user instances.

##### Integration with notmuch or mu4e

If you want to run notmuch or mu/mu4e after automatically synchronizing your mails, it is preferable to modify the above `mbsync.service` by adding a post-start hook, like below:

    ~/.config/systemd/user/mbsync.service

    [Unit]
    Description=Mailbox synchronization service

    [Service]
    Type=oneshot
    ExecStart=/usr/bin/mbsync -Va
    ExecStartPost=/usr/bin/notmuch new

You can also index `mu` by changing the `ExecStartPost` line to `ExecStartPost=/usr/bin/mu index`, or to `ExecStartPost=/usr/bin/emacsclient -e '(mu4e-update-index)'` if you are running emacsclient and would like to index `mu4e`.

This modification assumes that you have already setup notmuch or mu/mu4e for your user. If the ExecStart command does not execute successfully, the ExecStartPost command will not execute, so be aware of this!

Trigger syncing immediately when making local changes (such as marking messages as read) by watching the `.notmuch` directory:

    ~/.config/systemd/user/mbsync.path

    [Path]
    PathChanged=%h/mail/.notmuch

    [Install]
    WantedBy=default.target

Systemd defaults ensure that the service will not trigger redundantly.

#### With imapnotify

IMAP IDLE is a way to get push notifications to download new email, rather than polling the server intermittently. This has the advantage of saving bandwidth and delivering your mail as soon as it's available. Isync does not have native IDLE support, but we can use a program like imapnotify to call mbsync when you receive new email. For this example we will use the goimapnotify package which is reported to work better with frequent network interruptions.

Install goimapnotify and create a configuration file for each mail server you want to poll. Note that the file name format, including the .yaml, is necessary if you want to use the provided systemd service:

    ~/.config/imapnotify/gmail.yaml

    {
      "host": "imap.gmail.com",
      "port": 993,
      "tls": true,
      "tlsOptions": {
        "rejectUnauthorized": false
      },
      "username": "username@gmail.com",
      "password": "",
        "passwordCmd": "pass gmail | head -n1",
      "onNewMail": "mbsync gmail",
      "onNewMailPost": "",
      "boxes": [ "INBOX" ]
    }

(You can view the full configuration options in the project's README.)

Start/enable the `goimapnotify@gmail.service` user unit.

Note that IMAP IDLE only triggers when new mail arrives, not when there is undownloaded mail on the server. For example, if you receive 100 emails with your computer powered off, then turn on your computer, imapnotify will still not download new mail until you receive another email. For this reason you may want to run mbsync once when you log in.

### Using XOAUTH2

First install an XOAUTH2 SASL plugin, like cyrus-sasl-xoauth2-gitAUR.

For all OAuth2 helpers listed below, choose either one among them, you need to provide a `client_id` and optionally a `client_secret` of your own or of a suitable FOSS registered application.

In order to get a `client_id` and `client_secret`, you will need an app registration with the provider. You should create your own app registration if possible, otherwise, for example due to missing rights, you can use existing app registrations, such as Thunderbird's (under `kIssuers`) or Evolution's, which are publicly available until dynamic client registration is supported.

Another option is to temporarily use an incognito browser window to create a free outlook.com account and use that to create the app registration.

#### oama

oama is a utility which provides IMAP/SMTP clients with renewal capabilities and authorization of OAuth2 credentials. install oama-binAUR and configure it according to its README. You can find configuration templates in `/usr/share/oama`.

Before you are able to use oama with your credentials you need to authorize OAuth2 access by running the command below:

    $ oama authorize service email

Where service is your email provider (e.g. google) and email is your email address.

After the authorization completed add `AuthMechs XOAUTH2` and `PassCmd "oama access email"` to the `IMAPAccount` section in the `.mbsyncrc`.

#### oauth2token

Install oauth2tokenAUR and follow its README to configure the account. It will be responsible for getting the current XOAUTH2 token using the account credentials every time mbsync needs to authenticate.

Finally, add `AuthMechs XOAUTH2` and `PassCmd "oauth2get provider account"`, substituting `provider` and `account` with the values you used for `oauth2create`, to the `IMAPAccount` section in the `.mbsyncrc`.

#### mutt_oauth2.py

`mutt_oauth2.py` is known to work with Google and Microsoft accounts. Download mutt_oauth2.py (make it executable and put in your `PATH` if desired) and follow its README for background and to configure the account.

In short, you will need to modify the `ENCRYPTION_PIPE` and `DECRYPTION_PIPE` for your preferred encryption system directly in script's source or specify them on each subsequent renew invocation using flags. During authorization, add the `client_id` and `client_secret` from an app registration with the provider (see #Using XOAUTH2). Then to initialize your tokens, you run and answer the questions in:

    $ mutt_oauth2.py userid@myschool.edu.tokens --verbose --authorize

Note that gmail only supports the `localhostauthcode` authflow while MS only supports the `authcode` authflow.

To subsequently receive your access token (the script automatically handles renewing of tokens), you can run:

    $ mutt_oauth2.py userid@myschool.edu.tokens

As the `ENCRYPTION_PIPE` and `DECRYPTION_PIPE` options are not stored within the token file, you have to pass them separately if you do not want to hardcode your gpg key name in script's source:

    $ mutt_oauth2.py userid@myschool.edu.tokens --encryption-pipe 'gpg --encrypt --recipient <gpg-key>'

Finally, add `AuthMechs XOAUTH2` and `PassCmd "mutt_oauth2.py userid@myschool.edu.tokens"`, with the correct paths if necessary, to the `IMAPAccount` section in the `.mbsyncrc`.

#### oauth2ms

`oauth2ms` can be used to fetch oauth2 tokens from the Microsoft identity endpoint. Additionally, it can encode the token in the XOAUTH2 format to be used as authentication in IMAP mail servers.

Install `oauth2ms` as indicated and create a config file `$XDG_CONFIG_HOME/oauth2ms/config.json` containing the `client_id`.

Finally, add `AuthMechs XOAUTH2` and `PassCmd "oauth2ms"`, or the full path to `oauth2ms` if necessary, to the `IMAPAccount` section in `.mbsyncrc`.

### Integration with ProtonMail

Proton Mail solution for interfacing with conventional email clients is for the user to run a local IMAP/SMTP server that will communicate with ProtonMail servers -- it is known as ProtonMail Bridge and available in the protonmail-bridge-core package. Note that this software requires a running and working software implementing FreeDesktop.org's Secret Service API (e.g., GNOME Keyring or KeePassXC) and gpg-agent.

#### Bridge installation and configuration

1. Run the bridge and login using ProtonMail credentials:

       $ protonmail-bridge-core --cli
       >>> login
       >>> info

2. To let IMAP clients accessing the local Bridge IMAP server, get the ProtonMail self-signed certificate:

       $ openssl s_client -starttls imap -connect 127.0.0.1:1143 -showcerts

3. Manually copy lines between `-----BEGIN CERTIFICATE-----` and `-----END CERTIFICATE-----` and put them inside a file, e.g., `~/.config/protonmail/bridge-v3/cert.pem`.

4. After checking that everything is working, stop the Bridge from the command-line and run it as a service:

       $ systemctl --user enable --now protonmail-bridge.service

#### Isync configuration for interacting with Bridge

Configuring Isync to use ProtonMail Bridge as an IMAP server is possible using the following in your `~/.mbsyncrc` configuration. The following is a working example in a two-way sync between the local machine the ProtonMail account.

Note: In the following, only configuration that is special for ProtonMail will be commented.
Tip: The port can be obtained from the CLI interface of the ProtonMail Bridge binary.
Tip: In `Patterns`, we ignore the `Labels/*` directories since this is a directory hierarchy used internally by ProtonMail to store the labels/tags user settings.
Warning: In `Patterns`, we ignore the `All Mail/*` directory since this is a virtual view of all emails created by ProtonMail. As such, if not ignored, the IMAP library of Bridge (Gluon) will throw an error about an IMAP CLOSE command that is not allowed during the `Expunge` operation of Isync.

       IMAPStore proton-remote
       Port 1143
       Host 127.0.0.1
       User YOUR_EMAIL
       PassCmd YOUR_PASSWORD
       TLSType STARTTLS
       CertificateFile YOUR_CERTIFICATE_PATH

       MaildirStore proton-local
       SubFolders Verbatim
       Path ~/PATH/TO/MAILBOX/
       Inbox ~/PATH/TO/MAILBOX/Inbox

       Channel proton
       Far :proton-remote:
       Near :proton-local:
       Patterns * !Labels* !"All Mail"
       Create Both
       Expunge Both
       SyncState *

## Troubleshooting

### SSL error

If you get the following error:

    SSL error connecting imap.gmail.com (108.177.125.109:993): self signed certificate

Since google enforce SNI when you use TLS 1.3, ensure to run at least isync v1.3.0 See https://sourceforge.net/p/isync/isync/merge-requests/2/ for more details

If you get certificate related errors like:

    SSL error connecting pop.mail.com (193.222.111.111:143): error:00000012:lib(0):func(0):reason(18)

you may need to retrieve the server's certificates manually in order for mbsync to correctly verify it.

#### Step #1: Get the certificates

The factual accuracy of this article or section is disputed.

Reason: This may not always be needed, e.g. for gmail `CertificateFile /etc/ssl/certs/ca-certificates.crt` in the config file may be suffcient (Discuss in Talk:Isync#Step #1: Get the certificates)

    $ mkdir ~/.cert
    $ openssl s_client -connect some.imap.server:port -showcerts 2>&1 < /dev/null | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sed -ne '1,/-END CERTIFICATE-/p' > ~/.cert/some.imap.server.pem

This will create a certificate file called `~/.cert/some.imap.server.pem` (e.g. `~/.cert/imap.gmail.com.pem`). Alternatively one can download get_certs.sh and run it:

    $ mkdir ~/.cert
    $ wget https://gist.githubusercontent.com/petRUShka/af96ae25ce8280729b9ea049b929f31d/raw/a79471ce8aee3f6d04049039adf870a53a524f7f/get_certs.sh
    $ sh get_certs.sh some.imap.server port ~/.cert/

If you wish to do this manually, you may enter:

    $ openssl s_client -connect some.imap.server:port -showcerts

and it will display output something like:

    CONNECTED(00000003)
    depth=1 C = US, O = Google Inc, CN = Google Internet Authority
    verify error:num=20:unable to get local issuer certificate
    verify return:0
    ---
    Certificate chain
     0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=imap.gmail.com
       i:/C=US/O=Google Inc/CN=Google Internet Authority
    -----BEGIN CERTIFICATE-----
    MIIDgDCCAumgAwIBAgIKO3MmiwAAAABopTANBgkqhkiG9w0BAQUFADBGMQswCQYD
    VQQGEwJVUzETMBEGA1UEChMKR29vZ2xlIEluYzEiMCAGA1UEAxMZR29vZ2xlIElu
    dGVybmV0IEF1dGhvcml0eTAeFw0xMjA5MTIxMTU1NDlaFw0xMzA2MDcxOTQzMjda
    MGgxCzAJBgNVBAYTAlVTMRMwEQYDVQQIEwpDYWxpZm9ybmlhMRYwFAYDVQQHEw1N
    b3VudGFpbiBWaWV3MRMwEQYDVQQKEwpHb29nbGUgSW5jMRcwFQYDVQQDEw5pbWFw
    LmdtYWlsLmNvbTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEA2OmU9DjI+DFQ
    ThqIN4vL6EqZbzH0ejLKcc+zhxsq9BU5hXohSJ1sS5FUU2vReDKk8fd+ZR3cWtpf
    CTYAUSvdnz1ZFjESSzyUBmGRqByhoc0yqdfb61NosA4CDaO+z7DtAgKyecqnAJad
    TPYYf9aLk/UgJuc6GseitjzFYonXi6ECAwEAAaOCAVEwggFNMB0GA1UdJQQWMBQG
    CCsGAQUFBwMBBggrBgEFBQcDAjAdBgNVHQ4EFgQUFuLyTg2NcsyaEESytZbLbQan
    YIowHwYDVR0jBBgwFoAUv8Aw6/VDET5nup6R+/xq2uNrEiQwWwYDVR0fBFQwUjBQ
    oE6gTIZKaHR0cDovL3d3dy5nc3RhdGljLmNvbS9Hb29nbGVJbnRlcm5ldEF1dGhv
    cml0eS9Hb29nbGVJbnRlcm5ldEF1dGhvcml0eS5jcmwwZgYIKwYBBQUHAQEEWjBY
    MFYGCCsGAQUFBzAChkpodHRwOi8vd3d3LmdzdGF0aWMuY29tL0dvb2dsZUludGVy
    bmV0QXV0aG9yaXR5L0dvb2dsZUludGVybmV0QXV0aG9yaXR5LmNydDAMBgNVHRMB
    Af8EAjAAMBkGA1UdEQQSMBCCDmltYXAuZ21haWwuY29tMA0GCSqGSIb3DQEBBQUA
    A4GBAC1LV7tM6pcyVJLcwdPml4DomtowsjTrqvy5ZFa3SMKANK0iZBgFu74O0THX
    8SxP/vn4eAs0yRQxcT1ZuoishLGQl5NoimLaQ4BGQnzFQHDJendfaVKDl21GenJp
    is72sIrAeprsVU8PbNsllUamWsIjKr3DH5xQdH54hDtzQojY
    -----END CERTIFICATE-----
     1 s:/C=US/O=Google Inc/CN=Google Internet Authority
       i:/C=US/O=Equifax/OU=Equifax Secure Certificate Authority
    -----BEGIN CERTIFICATE-----
    MIICsDCCAhmgAwIBAgIDC2dxMA0GCSqGSIb3DQEBBQUAME4xCzAJBgNVBAYTAlVT
    MRAwDgYDVQQKEwdFcXVpZmF4MS0wKwYDVQQLEyRFcXVpZmF4IFNlY3VyZSBDZXJ0
    aWZpY2F0ZSBBdXRob3JpdHkwHhcNMDkwNjA4MjA0MzI3WhcNMTMwNjA3MTk0MzI3
    WjBGMQswCQYDVQQGEwJVUzETMBEGA1UEChMKR29vZ2xlIEluYzEiMCAGA1UEAxMZ
    R29vZ2xlIEludGVybmV0IEF1dGhvcml0eTCBnzANBgkqhkiG9w0BAQEFAAOBjQAw
    gYkCgYEAye23pIucV+eEPkB9hPSP0XFjU5nneXQUr0SZMyCSjXvlKAy6rWxJfoNf
    NFlOCnowzdDXxFdF7dWq1nMmzq0yE7jXDx07393cCDaob1FEm8rWIFJztyaHNWrb
    qeXUWaUr/GcZOfqTGBhs3t0lig4zFEfC7wFQeeT9adGnwKziV28CAwEAAaOBozCB
    oDAOBgNVHQ8BAf8EBAMCAQYwHQYDVR0OBBYEFL/AMOv1QxE+Z7qekfv8atrjaxIk
    MB8GA1UdIwQYMBaAFEjmaPkr0rKV10fYIyAQTzOYkJ/UMBIGA1UdEwEB/wQIMAYB
    Af8CAQAwOgYDVR0fBDMwMTAvoC2gK4YpaHR0cDovL2NybC5nZW90cnVzdC5jb20v
    Y3Jscy9zZWN1cmVjYS5jcmwwDQYJKoZIhvcNAQEFBQADgYEAuIojxkiWsRF8YHde
    BZqrocb6ghwYB8TrgbCoZutJqOkM0ymt9e8kTP3kS8p/XmOrmSfLnzYhLLkQYGfN
    0rTw8Ktx5YtaiScRhKqOv5nwnQkhClIZmloJ0pC3+gz4fniisIWvXEyZ2VxVKfml
    UUIuOss4jHg7y/j7lYe8vJD5UDI=
    -----END CERTIFICATE-----
    ---
    Server certificate
    subject=/C=US/ST=California/L=Mountain View/O=Google Inc/CN=imap.gmail.com
    issuer=/C=US/O=Google Inc/CN=Google Internet Authority
    ---
    No client certificate CA names sent
    ---
    SSL handshake has read 2108 bytes and written 350 bytes
    ---
    New, TLSv1/SSLv3, Cipher is ECDHE-RSA-RC4-SHA
    Server public key is 1024 bit
    Secure Renegotiation IS supported
    Compression: NONE
    Expansion: NONE
    SSL-Session:
        Protocol  : TLSv1.1
        Cipher    : ECDHE-RSA-RC4-SHA
        Session-ID: 77136647F42633D82DEDFBB9EB62AB516547A3697D83BD1884726034613C1C09
        Session-ID-ctx:
        Master-Key: 635957FBA0762B10694560488905F73BDD2DB674C41970542ED079446F27234E2CA51CF26938B8CA56DF5BBC71E429A7
        Key-Arg   : None
        PSK identity: None
        PSK identity hint: None
        SRP username: None
        TLS session ticket lifetime hint: 100800 (seconds)
        TLS session ticket:
        0000 - d6 5b a0 a7 10 0e 64 04-72 93 7c 9f 94 fa 07 57   .[....d.r.|....W
        0010 - f1 8b 9d 24 8b 9d 1b f3-a8 b1 4d 2c a9 00 e1 82   ...$......M,....
        0020 - 00 83 1e 3f e5 f2 b2 2c-d2 a8 87 83 16 02 0d 1e   ...?...,........
        0030 - bf b6 c1 d6 75 21 04 e6-63 6b ab 5b ed 94 7a 30   ....u!..ck.[..z0
        0040 - 1a d0 aa 44 c2 04 9b 10-06 28 b5 7b a0 43 a6 0d   ...D.....(.{.C..
        0050 - 3b 4a 85 1f 2e 07 0a e1-32 9b bd 5d 65 41 4c e2   ;J......2..]eAL.
        0060 - 7c d7 43 ec c4 18 77 53-b5 d4 84 b4 c9 bd 51 d6   |.C...wS......Q.
        0070 - 2d 4f 2e 10 a6 ed 38 c5-8e 9d f8 8b 8a 63 3f 7b   -O....8......c?{
        0080 - ee e6 b8 bf 7a f8 b8 e8-47 92 84 f1 9b 0c 63 30   ....z...G.....c0
        0090 - 76 d8 e1 44                                       v..D

        Start Time: 1352632558
        Timeout   : 300 (sec)
        Verify return code: 20 (unable to get local issuer certificate)
    ---
    * OK Gimap ready for requests from 108.78.162.240 o67if11168976yhc.67

Simply copy the first block that begins with `-----BEGIN CERTIFICATE-----` and ends with `-----END CERTIFICATE-----`, paste into a file, and save with a .pem extension (this is necessary for the next step). Older instructions state that, with Gmail, both certificate blocks must be saved but on testing this was found to be unnecessary.

Now, copy the root issuer certificate to your local certificate folder. In this example (Gmail), the root issuer is Equifax Secure Certificate Authority. This certificate is included in the ca-certificates package.

    $ cp /usr/share/ca-certificates/mozilla/Equifax_Secure_CA.crt ~/.cert/Equifax_Secure_CA.pem

#### Step #2: Setup mbsync

Configure mbsync to use that certificate:

    ~/.mbsyncrc

    IMAPAccount gmail
    Host imap.gmail.com
    # ...
    CertificateFile ~/.cert/imap.gmail.com.pem

### BAD Command with Exchange 2003

When connecting to an MS Exchange 2003 server, there could be problems when using pipelining (i.e. executing multiple imap commands concurrently). Such an issue could look as follows:

    mbsync -V exchange

    >>> 9 SELECT "arch"^M
    * 250 EXISTS
    * 0 RECENT
    * FLAGS (\Seen \Answered \Flagged \Deleted \Draft $MDNSent)
    * OK [PERMANENTFLAGS (\Seen \Answered \Flagged \Deleted \Draft $MDNSent)] Permanent flags
    * OK [UNSEEN 241] Is the first unseen message
    * OK [UIDVALIDITY 4352] UIDVALIDITY value
    9 OK [READ-WRITE] SELECT completed.
    >>> 10 UID FETCH 1:1000000000 (UID FLAGS)^M
    * 1 FETCH (UID 1 FLAGS (\Seen \Answered))
    * 2 FETCH (UID 2 FLAGS (\Seen \Answered))
    ...
    * 249 FETCH (UID 696 FLAGS ())
    * 250 FETCH (UID 697 FLAGS (\Seen))
    10 OK FETCH completed.
    >>> 11 APPEND "arch" (\Seen) {4878+}^M
    (1 in progress) >>> 12 UID FETCH 697 (BODY.PEEK[])^M
    (2 in progress) >>> 13 UID STORE 696 +FLAGS.SILENT (\Deleted)^M
    12 BAD Command is not valid in this state.

So command 9 is to select a new folder, command 10 checks the mail and commands 11, 12 and 13 run in parallel, writing/getting/flagging a mail. In this case, the Exchange server would terminate the connection after the BAD return value and go on to the next channel. (And if all went well in this channel, mbsync would return with 0.) After setting

    PipelineDepth 1

in the IMAPStore config part of the Exchange, this problem did not occur any more.

### Emails on remote server have the wrong date

This fix works when syncing with fastmail, but it likely applies to other services as well.

If you move an email to a new folder using an email client, and mbsync causes the email to appear with the wrong date on the server, add this to your configuration file:

    CopyArrivalDate yes

For example, without this setting, moving an old email from Inbox to Archive using mu4e and then syncing to fastmail with mbsync will cause the email to appear in Archive but with the date of the sync.

mbsync uses mtime of email message when uploading from maildir to imap server. You can use fix_maildir_mail_mtime.py script to set mtime from email header.

## External links

- Home page
- Sourceforge page
- backing up gmail with mbsync
- How To Verify SSL Certificate From A Shell Prompt

Categories:

- Mail retrieval agents
- OpenPGP

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