---
publish: true
permalink: /apps/isync
title: isync (mbsync)
created: 2026-01-30T08:09:43.461-07:00
modified: 2026-02-05T12:16:17.112-07:00
tags:
  - email
  - sync
  - imap
cssclasses: ""
---

isync (command: `mbsync`) is a tool for synchronizing IMAP mailboxes with local Maildir folders. Essential for offline email access with clients like [[10-19 LIFE/13 TECH SETUP/13.11 APPS/aerc]] or mutt.

## Installation

**Arch Linux:**
```bash
sudo pacman -S isync
```

## ProtonMail Integration

ProtonMail requires the Proton Bridge app for IMAP access. See the [Arch Wiki guide](https://wiki.archlinux.org/title/Isync#Integration_with_ProtonMail) for details.

### Setup with Proton Bridge

1. Install and run Proton Bridge
2. Get credentials from Bridge (it generates local IMAP/SMTP credentials)
3. Configure mbsync as below

## Configuration

`~/.mbsyncrc`:
```ini
# Global settings
Create Both
Remove Both
Expunge Both
SyncState *

# ProtonMail via Proton Bridge
IMAPAccount proton
Host 127.0.0.1
Port 1143
User your-email@proton.me
PassCmd "cat ~/.config/proton-bridge/password"
SSLType STARTTLS
CertificateFile ~/.config/proton-bridge/cert.pem

IMAPStore proton-remote
Account proton

MaildirStore proton-local
Path ~/.local/share/mail/proton/
Inbox ~/.local/share/mail/proton/INBOX
SubFolders Verbatim

Channel proton
Far :proton-remote:
Near :proton-local:
Patterns *
```

## Usage

```bash
# Sync all configured channels
mbsync -a

# Sync specific channel
mbsync proton

# Verbose output
mbsync -V proton

# Dry run (show what would happen)
mbsync -n proton
```

## Automation

### systemd timer
`~/.config/systemd/user/mbsync.timer`:
```ini
[Unit]
Description=Sync mail periodically

[Timer]
OnBootSec=1m
OnUnitActiveSec=5m

[Install]
WantedBy=timers.target
```

`~/.config/systemd/user/mbsync.service`:
```ini
[Unit]
Description=Sync mail

[Service]
Type=oneshot
ExecStart=/usr/bin/mbsync -a
```

Enable:
```bash
systemctl --user enable --now mbsync.timer
```

## Tips

- Create the local maildir first: `mkdir -p ~/.local/share/mail/proton`
- Use `PassCmd` to avoid storing passwords in config
- The `Patterns *` line syncs all folders; use specific patterns to limit
- Check sync status with `mbsync -V` for verbose output