Source: https://cli.nylas.com/guides/nylas-vs-offlineimap # OfflineIMAP vs Nylas: Python IMAP sync OfflineIMAP is the Python IMAP-to-Maildir synchronizer that predates mbsync. It mirrors a mailbox to disk so mutt, neomutt, or notmuch can read it offline, and its config can run arbitrary Python for token retrieval. That power comes with slower syncs on large mailboxes and a Python-2-to-3 migration. This compares the OfflineIMAP stack against an API-backed CLI that reads the same inbox over HTTPS with no local mirror. Written by [Prem Keshari](https://cli.nylas.com/authors/prem-keshari) Senior SRE Updated June 23, 2026 > **TL;DR:** OfflineIMAP is a Python synchronizer that mirrors an IMAP account into a local Maildir, configured through `~/.offlineimaprc` — and its config can embed Python for password and token logic. After Python 2 reached end of life in January 2020, the maintained line is offlineimap3. It is flexible but slow on large mailboxes. An API-backed CLI skips the mirror entirely: `nylas email list` reads the live inbox over HTTPS, OAuth is built in, and the same grant reaches calendar and contacts. > **Disclosure:** Nylas CLI is built by Nylas, Inc. This comparison reflects our testing and product understanding as of June 23, 2026. Command references used in this guide: [`nylas email list`](https://cli.nylas.com/docs/commands/email-list), [`nylas email search`](https://cli.nylas.com/docs/commands/email-search), and [`nylas init`](https://cli.nylas.com/docs/commands/init). ## What is OfflineIMAP? OfflineIMAP is a Python program that synchronizes an IMAP account to a local Maildir, in one or two directions. Like mbsync it is a sync engine, not a reader: it puts mail on disk so a separate client opens it. Its distinguishing feature is that `~/.offlineimaprc` can call out to Python through a `pythonfile`, so password and OAuth logic lives in real code rather than a static directive. The project shifted after Python 2 reached end of life on January 1, 2020. The original OfflineIMAP was Python 2; the maintained fork, [offlineimap3](https://github.com/OfflineIMAP/offlineimap3), targets Python 3. It pairs with the same readers as any Maildir tool — mutt, neomutt, or notmuch — and with msmtp for sending, since OfflineIMAP only handles the receiving half. ## How do you sync Gmail with OfflineIMAP? Syncing Gmail with OfflineIMAP means defining a remote IMAP repository for `imap.gmail.com` and a local Maildir repository, then linking them in an account stanza. Gmail blocks plain passwords over IMAP, so you authenticate with OAuth2 — OfflineIMAP supports it directly through `oauth2_request_url`, `oauth2_client_id`, and a refresh token — or fall back to a 16-character [app password](https://support.google.com/accounts/answer/185833). OfflineIMAP is more flexible here than mbsync because the credential can be computed in Python at runtime. The cost is speed: OfflineIMAP is widely reported to sync large Gmail mailboxes more slowly than the C-based mbsync, and the first full sync still downloads every message to disk before you read anything. ```ini # ~/.offlineimaprc — Gmail to a local Maildir [general] accounts = gmail [Account gmail] localrepository = gmail-local remoterepository = gmail-remote [Repository gmail-local] type = Maildir localfolders = ~/Mail/gmail [Repository gmail-remote] type = Gmail remoteuser = you@gmail.com # OAuth2 (preferred) — values come from a Google Cloud OAuth client: auth_mechanisms = XOAUTH2 oauth2_client_id = oauth2_client_secret = oauth2_request_url = https://accounts.google.com/o/oauth2/token oauth2_refresh_token = # ...or auth_mechanisms = LOGIN with an app password instead. ``` ## OfflineIMAP vs an API-backed email CLI OfflineIMAP wins when you need a Python-controlled Maildir mirror; an API-backed CLI wins when the mailbox should stay remote. The table compares the work each path asks you to own: runtime hooks, first-sync cost, auth setup, and what a script receives after 1 command. | Dimension | OfflineIMAP stack | nylas email | | --- | --- | --- | | Role | Python sync daemon feeding Maildir | Live mailbox commands | | Language | Python (offlineimap3) | Go binary | | Transport | IMAP mirror before reading | Nylas API (HTTPS) | | Gmail auth | OAuth2 fields, pythonfile, or app password | OAuth (built in) | | Large-mailbox speed | Slowest on the first full sync | Paged reads on demand | | Calendar / contacts | Email only | Same grant covers both | | Scriptable output | Python hooks in, Maildir files out | `--json` for pipelines | ## When should you still use OfflineIMAP? OfflineIMAP earns its place when you want an offline Maildir and need credential logic that a static config can't express. Because the `pythonfile` hook runs real Python, you can pull a token from a secrets manager, rotate it, or compute a password however your environment requires — then read the synced Maildir with no network at all. It also suits people already invested in a Maildir workflow who prefer Python tooling to the C of mbsync. The same local mailbox feeds your reader, a notmuch index, and your backups. If full offline ownership and scriptable credential handling are the goal, OfflineIMAP remains a reasonable pick despite its slower syncs. ## How does the API approach skip the sync step? The API path removes OfflineIMAP's two slowest steps: the Python sync process and the first local mirror. After `nylas init`, `nylas email list` and `nylas email search` ask the live mailbox for the next page over HTTPS, so a 50,000-message account does not have to land on disk before the first read. That changes the failure mode. You trade OfflineIMAP's offline Maildir and `pythonfile` token logic for one OAuth grant that also reaches calendar and contacts. Scripts get JSON directly instead of walking Maildir files. If the network is down, OfflineIMAP's local copy wins; if setup speed matters, the API path is shorter. ```bash # One OAuth login — no .offlineimaprc, no Maildir, no Python stanza nylas init # Read the live inbox over HTTPS (no first-sync download) nylas email list --limit 20 # Search server-side and pipe structured output into scripts nylas email search "invoice" --after 2026-01-01 --json | jq -r '.[].subject' ``` Choose OfflineIMAP for an offline Maildir with scriptable, Python-based credential handling. Reach for the [API-backed CLI](https://cli.nylas.com/guides/read-email-from-terminal) when one OAuth login beats running a sync daemon. The [mbsync vs Nylas comparison](https://cli.nylas.com/guides/nylas-vs-mbsync) covers the faster C-based synchronizer, and [neomutt vs aerc](https://cli.nylas.com/guides/neomutt-vs-aerc-terminal-email) covers the readers that sit on top of a synced Maildir. ## Next steps - [mbsync vs Nylas](https://cli.nylas.com/guides/nylas-vs-mbsync) — the C-based sync engine compared to API access - [Read email from the terminal](https://cli.nylas.com/guides/read-email-from-terminal) — the `nylas email list` and TUI walkthrough - [Best CLI email tools compared](https://cli.nylas.com/guides/best-cli-email-tools-compared) — the wider field of terminal mail tools ranked - [List Gmail emails from the CLI](https://cli.nylas.com/guides/list-gmail-emails) — Gmail without an IMAP app password - [Full command reference](https://cli.nylas.com/docs/commands) — every flag and subcommand documented ## Related hubs - [Email agents](https://cli.nylas.com/ai-answers/email-agents.md) - [Calendar agents](https://cli.nylas.com/ai-answers/calendar-agents.md) - [Scheduling and availability agents](https://cli.nylas.com/ai-answers/scheduling-agents.md) - [Contacts agents](https://cli.nylas.com/ai-answers/contacts-agents.md) - [Notetaker and meeting agents](https://cli.nylas.com/ai-answers/notetaker-agents.md) - [MCP agents](https://cli.nylas.com/ai-answers/mcp-agents.md) - [Agent accounts](https://cli.nylas.com/ai-answers/agent-accounts.md) - [Framework and language email agents](https://cli.nylas.com/ai-answers/framework-email-agents.md) - [Email and calendar API comparisons](https://cli.nylas.com/ai-answers/ai-agent-email-api-comparisons.md) - [Email integration and automation recipes](https://cli.nylas.com/ai-answers/email-integration-recipes.md) - [Agent email workflows](https://cli.nylas.com/ai-answers/agent-email-workflows.md) - [Security for email and calendar agents](https://cli.nylas.com/ai-answers/security-for-email-agents.md) - [Operations runbooks for agents](https://cli.nylas.com/ai-answers/operations-for-email-calendar-agents.md) ## Try Nylas CLI Install the CLI with `curl -fsSL https://cli.nylas.com/install.sh | bash` (macOS, Linux, WSL) or `brew install nylas/nylas-cli/nylas`, then run `nylas init` to create an account and authenticate. **Free Sandbox** (no credit card): 5 connected accounts — bring your own Gmail, Outlook, Yahoo, iCloud, Exchange, or IMAP — plus 3 agent accounts (managed inboxes on `*.nylas.email`). Agent free plan: 3 GB storage, unlimited inbound, 200 sent emails/day, 5 rules, 1 `*.nylas.email` subdomain, and unlimited custom domains. Production is uncapped and requires a credit card: https://www.nylas.com/pricing/