Imapsync

Imapsync#

Imapsync is an IMAP transfer tool used for copying and moving emails between IMAP servers.

While Imapsync has a wide range of use cases, the NS8 Imapsync application focuses on transferring emails from remote IMAP servers to a Mail application instance. It serves two main purposes:

  1. IMAP account migration: Messages from a remote IMAP account can be imported to a local Mail account. The import is recursive, incremental, and can be repeated as needed.

  2. INBOX retrieval: Messages received in the INBOX folder of a remote IMAP account can be periodically transferred to the INBOX folder of a local Mail account. See Understanding “Only INBOX” option for details on how this process works.

Configuration#

Imapsync must be configured to use an existing Mail module in the NethServer 8 cluster. For this purpose, it must be granted master user access to the Mail module. Navigate to the Settings page and select a Mail instance from the drop-down menu.

Once configured, proceed to the Tasks page and create one or more synchronization tasks. Click Create task and complete the form fields as follows:

  • Local user: Select the NS8 user account that will receive the synchronized emails.

  • Remote user: Enter the username or email address to authenticate with the remote IMAP server.

  • Remote password: Provide the password for the remote IMAP account. Click the eye icon to reveal the password if needed.

  • IMAP server: Enter the hostname or IP address of the remote IMAP server (e.g., imap.example.org).

  • IMAP TCP Port: Specify the port number for the IMAP server:

    • 143 (default) for STARTTLS encryption

    • 993 for SSL/TLS encryption

  • Select encryption: Choose the encryption method required by the remote IMAP server:

    • STARTTLS (default 143/tcp): Upgrades an unencrypted connection to a secure one.

    • SSL/TLS (993/tcp): Uses an encrypted connection from the start.

    • None: Connects without encryption (not recommended).

  • Folder synchronization: Choose which folders to sync from the remote server:

    • Only INBOX: Synchronizes only the main inbox. This option enables the user’s Sieve filter to process messages during each task run. See Understanding “Only INBOX” option for a detailed explanation.

    • All folders: Synchronizes all available folders recursively.

    • All except selected: Synchronizes all folders except those specified. Enter one folder name per line in the text area. The entries are interpreted as Regular Expressions matching remote folder names.

  • Remote server messages deletion: Configure how messages should be handled on the remote server after synchronization:

    • Do not delete any message (default)

    • Delete messages from the server after each sync

    • Delete messages older than a specified number of days (a field will appear to specify the retention period)

  • Task frequency: Define how often the task runs:

    • Not scheduled, manual execution only: Runs only when manually triggered.

    • Run at a fixed interval (in minutes): Runs automatically at the specified interval.

Once all fields are set, click Create task to create the task. To discard the changes, click Cancel.

Understanding “Only INBOX” option#

Note

To avoid unexpected changes to the “Seen” flag required by Imapsync, do not access the remote IMAP account with other IMAP clients.

When a message is transferred by a task using the Only INBOX folder synchronization option, it is marked in the remote account with the IMAP “Seen” flag. IMAP clients commonly display messages without the “Seen” flag as “New” or “Unread.”

Messages with the “Seen” flag are ignored by Imapsync in subsequent transfers. This prevents re-transferring messages that have been moved from the local INBOX to Trash or another folder.

Using the “Seen” flag as a transfer condition also allows the user’s Sieve filter to be applied safely to transferred messages.

NethServer as a Remote IMAP Server#

If the remote IMAP server is a NethServer instance, you can configure the synchronization task using either a regular user account or the IMAP master user password. The master user simplifies migration by avoiding the need to know individual account passwords.

In NethServer 7 the vmail master user password can be retrieved at /var/lib/nethserver/secrets/vmail.

In NethServer 8 the vmail master user password can be obtained from a command like:

runagent -m mail1 grep DOVECOT_VMAIL_PASS dovecot.env

Append the *vmail suffix to the task’s Remote user field value.

For example:

  • ns8user becomes ns8user*vmail

  • ns7user@example.org becomes ns7user@example.org*vmail

Known limitations#

  • Messages copied by Imapsync bypass anti-spam and anti-virus checks. To ensure security, enable these protections on the remote IMAP server before synchronization.

  • Imapsync does not integrate with Piler, meaning that messages transferred via Imapsync are not archived.

  • Messages copied by Imapsync do not trigger the Dovecot vacation (out-of-office) auto-reply. If the local account has the vacation plugin enabled, remote senders will not receive an automatic vacation response, because messages delivered via Imapsync lack the envelope attributes required to properly compose and send the automated reply.

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