imapsync

Synchronize IMAP account between host1 and host2

$ imapsync --host1 [host1] --user1 [user1] --password1 [secret1] --host2 [host2] --user2 [user2] --password2 [secret2]

imapsync [options] --host1 host --user1 user --password1 pass --host2 host --user2 user --password2 pass

--host1 host
    Source IMAP server hostname or IP

--host2 host
    Destination IMAP server hostname or IP

--user1 user
    Source IMAP username

--user2 user
    Destination IMAP username

--password1 pass
    Source IMAP password (prompt if omitted)

--password2 pass
    Destination IMAP password (prompt if omitted)

--port1 port
    Source IMAP port (default 143)

--port2 port
    Destination IMAP port (default 143)

--ssl1
    Enable SSL on source server

--ssl2
    Enable SSL on destination server

--tls1
    Enable STARTTLS on source

--tls2
    Enable STARTTLS on destination

--folder folder
    Transfer specific folder (repeatable)

--folderrec folder
    Recursively transfer folders

--subscribed
    Sync only subscribed folders

--syncinternaldates
    Preserve internal message dates

--dry
    Dry run: simulate without copying

--delete
    Delete messages/folders on dest matching source deletions

--maxage days
    Sync messages newer than N days

--maxsize bytes
    Skip messages larger than N bytes

--justfolders
    Create folders only, no messages

--nofoldersizes
    Don't check folder sizes

--regextransf regex
    Regex for folder name transforms

--authmech1 mech
    Source auth mechanism (PLAIN, LOGIN, etc.)

--buffersize bytes
    I/O buffer size (default 8MB)

--pidfile file
    PID file for daemon mode

--help
    Show full usage

--version
    Print version

imapsync is a powerful command-line utility written in Perl for transferring and synchronizing email messages between two IMAP4 servers. It enables seamless mailbox migrations, backups, or ongoing syncs without interrupting service. Key features include recursive folder copying, message filtering by date/size/flags, deletion synchronization, and preservation of internal dates, flags, labels, and ACLs. It supports SSL/TLS, authentication methods like CRAM-MD5 and DIGEST-MD5, and handles duplicates via unique identifiers (UIDs). Ideal for server migrations, consolidations, or replicating mailboxes across providers like Gmail, Outlook, or self-hosted setups. Usage is straightforward: specify source and destination server credentials, select folders, and run. Dry-run mode (--dry) allows testing without changes. For large mailboxes, it resumes interrupted transfers and throttles connections to avoid overwhelming servers. Despite its age, it remains a go-to tool due to reliability and minimal dependencies.

Resource-intensive for millions of emails; requires Perl modules (IO::Socket::SSL, etc.); single-threaded, so slow on very large accounts; potential issues with proprietary IMAP extensions (e.g., Gmail labels); use --timeout to handle slow connections; not actively maintained since author's passing in 2022.

Available via apt (apt install imapsync), yum, or Perl CPAN: cpan App::Imapsync. Requires Mail::IMAPClient and other modules.

imapsync --host1 imap.old.com --user1 user@old --password1 pass1 --host2 imap.new.com --user2 user@new --password2 pass2 --folderrec Inbox --syncinternaldates
Dry-run first with --dry.

Developed by Gilles Lamiral starting in 2001 as a Perl script for IMAP syncing. Gained popularity for migrations in early 2000s hosting era. Reached version 2.x by 2020s with thousands of downloads. Archived post-2022 due to author's death, but forks like imapsync-community continue enhancements.

offlineimap(1), mbsync(1), doveadm-sync(1), mutt(1)