ImapSync vs. MigrationWiz

ImapSync is a command-line tool which can be used to migrate IMAP content between mailboxes. We’ve had a few customers ask us if they could use ImapSync as a cheaper alternative. Here is our answer.

ImapSync wasn’t optimized for speed. For starters, it was written in Perl, a scripting language which by default is interpreted, not compiled. There is plenty of evidence supporting this:

  • “284 MINUTES for just 404 messages (4mb)!” (source)
  • “Way too slow for my needs” (source)
  • “imapsync is slow” (source)
  • “Imapsync is definitely the biggest hog in the migration process” (source)
  • “Too bad it’s that slow” (source)
  • “it never finishes syncing the whole mailbox, which is around 7.7GB” (source)

MigrationWiz migrates from and to most IMAP servers with speeds in excess of 1GB / hour / mailbox. What makes the difference? Better engineering and a better infrastructure. We employ several techniques such as batching, queuing, parallelization, compression, caching, or adaptive retries. We’re also connected to one of the fastest hub on the planet.

ImapSync was created by a single developer. As with every shrink-wrapped software solution, crashes and other bugs can be fixed. However it requires users to provide detailed error reports, and  the developer to diligently reproduce and fix the issue. Once an update becomes available, it must be downloaded and deployed.

  • Google search for “imapsync” and “hangs”:  2190 results
  • Google search for “imapsync” and “crashes”:  5850 results

MigrationWiz runs a cloud migration service which means we get to witness and fix every problem our customers encounter. Because we run the migration infrastructure, we cannot afford to run servers which crash, hang, or run inefficiently. What we sell are migrations, not a migration executable. If a migration fails, we don’t get paid.

With imapsync, you may need a lot of powerful machines to perform a large-scale migration. Some people have attempted to write scripts which distribute imapsync migrations to multiple machines. Unfortunately not only is the approach complex, it is also error-prone. From this article:

“I got about 142 hours of syncing done in about 24 hours of clock time by running 20 copies at once across 4 servers. I’ve since gone to 5 servers with 4 procs each. However, after a while, all the imapsyncs eventually hang”

MigrationWiz uses patent-pending technology to migrate a large number of mailboxes by automatically allocating computing resources and distributing workload to these resources. All monitoring and reporting is centralized. We’ve sometimes used hundreds of computers to migrate a single large customer over a week end. There is no need to install or purchase any software or hardware.

The Windows version of imapsync.exe costs $25 without support and $125 with support. After your purchase is complete, you’ll receive a download link “in less than 24 hours” (source). While you can get some free support from the community, realize that paid support will probably all come from the author, an ex-Unix administrator based in France.

Check out our Pricing Page on our website, and see how our User Migration Bundle licence offers the best value bundling mailbox, documents, personal archives, and our automated, remote Outlook configuration tool. Migration licenses are available immediately after purchase which means you can purchase and configure a migration within minutes.

ImapSync dumps migration results to a raw log file. You’re responsible for analyzing log files to determine what failed to migrate and for what reason. The same applies to progress monitoring: you’ll need to periodically open log file to understand what is happening.

With MigrationWiz, you get easy-to-understand statistics including visual graphs and charts. Everything is available on the web using a simple browser. You can also configure email alerts and notifications. Errors are reported in a comprehensible way and linked to KB articles explaining why an item failed to migrate. You can also export stats to CSV files.

Other Issues:

  • ImapSync only supports IMAP-to-IMAP migrations. MigrationWiz also supports Google Apps, Exchange,, etc.
  • ImapSync can fail to migrate items without a header. MigrationWiz does not require headers in order to migrate items.
  • ImapSync can fail to migrate items from Gmail due to SSL library problems. MigrationWiz has migrated thousands of terabytes from Gmail.

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