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OfflineIMAP vs lieer: catalog facts
OfflineIMAP	lieer
Free Free and open source under the GPL.	Free Free and open source under the GPL-3.0 or later.
macOS, Linux, Command line	macOS, Linux, Command line
Two-way sync into plain Maildir, which any local mail client can read Per-folder rules and filters for what gets mirrored	Two-way sync between Gmail labels and notmuch tags Keeps a full local maildir copy of the mailbox
Python performance is poor on very large mailboxes Configuration is a hand-written file with many options	Only works with Gmail accounts Requires notmuch and command-line setup
Downloadable app	Downloadable app
Open source	Open source
License: GPL-2.0	License: GPL-3.0-or-later
Not stated if an account is needed	Account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked October 1, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.