Backing Up Business Email: IMAP Export, Archives, Restore Tests

Your mail provider keeps your mailboxes running; it does not promise to keep a copy of the message you deleted last month, the mailbox a leaver emptied, or your data if your account is suspended or your domain lapses. A backup you control, stored somewhere else, is the only protection against those. Because every business mailbox speaks IMAP, you do not need special software to make one.

Quick answer

Connect each mailbox over IMAP to a desktop client or a command-line sync tool, download every folder to local storage, and copy the result to a second location such as encrypted external storage or a separate cloud account. Run it monthly (weekly for finance mailboxes), keep at least three months of versions, and once a quarter open a backup and prove you can read and restore a message.

Method 1: a desktop mail client (simplest)

1. Install Thunderbird (free, cross-platform) on a machine that will stay on for the job.
2. Add each mailbox as an IMAP account. For OquMail: server mail.oqumail.com, port 993, SSL/TLS, username is the full address; outgoing mail.oqumail.com, port 587, STARTTLS.
3. In the account's synchronisation settings, choose to keep messages for this account on this computer, for all folders, so full copies are downloaded rather than headers only.
4. Let it sync. A 5 GB mailbox can take a while on the first pass; later passes only fetch changes.
5. Export. Thunderbird stores each folder as an mbox file inside its profile directory; copy the profile's Mail or ImapMail folder to your backup location. The ImportExportTools NG add-on can also export folders to mbox or EML files on demand.

Method 2: a sync tool (better for schedules)

Command-line tools such as imapsync, OfflineIMAP, or mbsync (isync) pull a mailbox to local Maildir or mbox storage and can be run on a schedule with Task Scheduler on Windows or cron on macOS and Linux. They are the standard way to back up several mailboxes without a desktop app open, and imapsync in particular is widely used for migrations between providers. Store credentials in the tool's supported secure file, not in the script.

Where to keep the backup

• Not on the same computer that runs the mail client, or a hardware failure takes both.
• An encrypted external drive kept off-site, or a second cloud storage account with its own login and two-factor authentication.
• Encrypt the archive. Mbox and Maildir are plain text; anyone who obtains the drive reads every message. Full-disk encryption on the drive, or a 7-Zip archive with AES-256, is enough.
• Keep versions. A single overwritten backup cannot recover a message deleted before last night's run. Retain monthly snapshots for as long as your retention policy requires.

Test the restore, every quarter

1. Pick a random month and a random mailbox from the backup.
2. Open the mbox in Thunderbird (via a local folder import) or read the Maildir with any compatible client.
3. Find a specific message by subject and confirm the attachment opens.
4. Restore it to the live mailbox by dragging it into an IMAP folder, then delete the test copy.
5. Record the date and outcome. A backup you have never restored is a hope, not a backup.

What to back up beyond the mailboxes

• Your DNS zone: export the records so MX, SPF, DKIM, and DMARC can be recreated quickly at a new DNS host.
• Your mail provider's settings: mailbox list, aliases, forwarding rules, and API keys in use, so a rebuild is not from memory.
• Contacts and signatures, which live in mail clients rather than on the IMAP server.

Mistakes to avoid

• Backing up headers only. Check the client's offline-storage setting downloads full bodies.
• Relying on "the provider has backups". Provider backups protect the provider's service, not your deleted message or suspended account.
• Backing up to a folder inside the same account, or to the leaver's laptop.
• Never testing. Corrupt mbox files and half-finished syncs are common and invisible until you need them.

Common questions

How big will the backup be?

Roughly the mailbox size, so up to 5 GB per OquMail mailbox on the free plan. Mbox files compress well; expect archives to be 30 to 60 percent of the live size.

Can I back up webmail-only accounts?

If the provider offers IMAP, yes, and OquMail does for every mailbox. Providers without IMAP require their own export tool, which is a reason to prefer IMAP-capable hosting.

Should individuals back up their own mailboxes?

Better that the business does it centrally with one process and one storage location, so backups survive staff changes and are covered by the retention policy.