imapsync

imapsync is a focused utility for moving or backing up email between IMAP accounts. It best suits administrators and technically comfortable users handling staged or tenant-to-tenant mailbox work. Its durable, restartable transfers are compelling, but it is not a complete migration suite for every kind of account data.

Overview

Founded in 2001 and authored by Gilles Lamiral in Baulon, France, imapsync combines command-line software with a web-based synchronization option. Its central task is copying mail between IMAP mailboxes for migration or backup. The command-line program works incrementally and recursively, so a job can be stopped and resumed without producing duplicate messages. That is a meaningful operational advantage when a cutover must run in stages or a maintenance window ends unexpectedly.

The maker cites compatibility with Gmail, Office 365, Exchange, Dovecot and Zimbra, alongside general IMAP support. Tenant-to-tenant moves and staged migrations are supported, as are Microsoft 365 and Google Workspace environments. The scope is deliberately limited to mailbox content: contacts and calendars are not migrated, active accounts cannot be kept synchronized in both directions, and messages cannot be moved to or from a local directory.

Key features

Incremental, resumable transfers

Imapsync's strongest feature is its transfer behavior. Incremental comparison avoids treating each run as a full recopy, recursive handling covers mailbox folder structures, and duplicate-safe restarts make interrupted jobs recoverable. This favors administrators planning phased moves, backups or repeated synchronization rather than one-off manual copying.

Online and self-hosted options

The online service provides free mailbox syncs below 3 GB. Purchasing removes that size boundary and permits unlimited online syncs of any size through the bundled plan. Buyers also receive a visual interface that can be installed on a Linux server. That self-hosted interface is useful when a graphical workflow is preferred, but it does not currently run on Windows, so Windows users needing that interface must use the online service or command-line software instead.

Focused IMAP coverage

Windows, Mac OS X and Linux run the command-line software, while the product is also offered as web and self-hosted software. Support for common hosted and server-based IMAP systems makes it suitable for many business mailbox moves. It is a poor fit when the project includes address books, calendars, local mail archives or continuous two-way synchronization; those requirements need another product or a separate process.

Privacy and support

The service privacy policy says it may collect email addresses, cookies, usage data and diagnostic information, and it does not promise absolute data security. Organizations with strict handling rules should assess that exposure before choosing the online route. Paid professional support comes from the developer in English, mainly by email and possibly by phone or Skype, during office hours of 10:00–16:00 UTC.

Pricing

There is a free option, but no trial version. Purchases carry a 30-day money-back guarantee.

The free online allowance is practical for a mailbox under 3 GB, but larger or repeated online jobs require a purchase. Software only is the economical choice for operators who can manage migrations themselves and need unlimited use with lifetime updates. Professional support suits teams buying assistance without the software bundle. Imapsync + support costs the same one-time amount as support alone while adding the software and unlimited online syncs, making it the clearest option for customers who want both guided migration and the web service.

Platforms

Command-line software runs on Windows, Mac OS X and Linux. The product also has web and self-hosted forms; the visual self-hosted interface is installable on Linux servers only.

Who it's for

Choose imapsync for staged mailbox migrations, tenant-to-tenant moves and recurring IMAP backups where restartable, duplicate-resistant jobs matter. It is especially appropriate for administrators comfortable with command-line operation or willing to pay for developer support. Look elsewhere if a move must include calendars, contacts, local directories or live two-way account synchronization, or if a Linux-only self-hosted interface is unsuitable.

Pros and cons

Pros

• Incremental, recursive transfers can resume without creating duplicates, reducing risk during long or staged jobs.
• Broad compatibility includes Gmail, Office 365, Exchange, Dovecot, Zimbra, Microsoft 365, Google Workspace and standard IMAP.
• One-time software pricing includes unlimited use and lifetime updates.
• The paid bundle adds unlimited online syncs of any size and direct developer support.

Cons

• No calendar or contact migration, so it cannot deliver a complete account move.
• No two-way synchronization for two active accounts and no local-directory transfers.
• The free online service is limited to mailboxes below 3 GB.
• The graphical self-hosted interface works on Linux, not Windows.
• The online service may collect usage and diagnostic data and cannot guarantee absolute security.

Alternatives

See the Email Migration Software directory for more choices.

Zoho Mail is a better pick for a hosted mail service with a forever-free plan for five users, one domain and 5 GB per user, plus a free trial.

MailJerry suits users wanting a free migration allowance with unlimited mailboxes, 150 MB per mailbox and three simultaneous migrations on one device.

Cigati Email Migrator is aimed at Windows and macOS users who want a free demo covering the first 100 emails per folder before licensing unlimited migration.

imap-migrate is a free, cross-platform option for straightforward IMAP folder migration when Python 3.12 or newer is available on both sides.

SysTools Email Migration Tool offers a free full migration for up to two user accounts and a 35.00 USD paid version.

SysTools Migrator likewise starts with two free accounts and uses a 35.00 USD license quota based on migrated users.

CloudM Migrate is an alternative for broader cloud migration projects.

Inbox Hop is another paid option with a free plan.

Verdict

Imapsync is a strong choice for administrators who need dependable, resumable IMAP mailbox transfers, particularly for staged or tenant-to-tenant work. Its one-time software pricing, wide server compatibility and optional developer support reinforce that focused role. Look elsewhere when calendars, contacts, local mail, or ongoing two-way synchronization are essential, or when the Linux-only self-hosted interface is a constraint.