How to Archive Old Business Email Without Deleting Anything

Old email is evidence: what a client agreed to, what a supplier promised, what you told the tax office. Deleting it to tidy the inbox is a mistake you only discover when you need the message. Archiving keeps everything searchable while getting it out of the way. Here is how to do it on the server, on your computer, or both.

Quick summary

• Create a folder called Archive in webmail if your host has not already. On IMAP it appears in every mail app within a minute.
• Sort Inbox by date, select everything older than 90 days that is not flagged or in a Waiting folder, and move it to Archive. In webmail and most apps you can select a range with Shift-click.
• For a large backlog, move one year at a time. Moving 40,000 messages in one drag can time out on IMAP; a few thousand at a time is safe.
• From now on use the Archive button (the "E" shortcut in many webmail apps, Backspace in Outlook desktop) instead of Delete.
• Outlook desktop: File, Open and Export, Import/Export, "Export to a file", Outlook Data File (.pst). Choose the Archive folder and include subfolders. The result is one file you can store anywhere.

Archive means "moved", not "removed"

In every mainstream mail app, Archive moves a message out of Inbox into a folder that stays searchable. Nothing is deleted. The confusion comes from Outlook, which has two different things called archive: the Archive button, which moves a message to an Archive folder on the server, and AutoArchive, which copies old items into a local .pst file and removes them from the server. Know which one you are pressing.

Option 1: archive on the server (simplest)

1. Create a folder called Archive in webmail if your host has not already. On IMAP it appears in every mail app within a minute.
2. Sort Inbox by date, select everything older than 90 days that is not flagged or in a Waiting folder, and move it to Archive. In webmail and most apps you can select a range with Shift-click.
3. For a large backlog, move one year at a time. Moving 40,000 messages in one drag can time out on IMAP; a few thousand at a time is safe.
4. From now on use the Archive button (the "E" shortcut in many webmail apps, Backspace in Outlook desktop) instead of Delete.

Option 2: keep a local copy as well

• Outlook desktop: File, Open and Export, Import/Export, "Export to a file", Outlook Data File (.pst). Choose the Archive folder and include subfolders. The result is one file you can store anywhere.
• Thunderbird: install the ImportExportTools NG add-on, right-click a folder, Export folder as mbox. Mbox is a plain-text standard every mail app can read.
• Apple Mail: select a folder, Mailbox, Export Mailbox. Produces an .mbox package.
• Store the file with your other business records and make sure your normal backup covers it. A .pst on a laptop that dies is not an archive.

What to keep, and for how long

• Invoices, receipts, contracts and anything a tax authority could ask for: keep for your jurisdiction's statutory period, commonly five to seven years. Check your accountant's advice.
• Customer correspondence about a purchase or complaint: keep at least as long as any warranty, limitation period or dispute window.
• Newsletters, notifications, calendar invites: delete after 30 to 90 days. They have no evidential value.
• Personal-data requests under GDPR or similar laws may require you to find or erase a person's messages, so a searchable archive helps you comply rather than hindering it.

Storage is rarely the reason to delete

A typical business mailbox grows by a few hundred megabytes a year unless people email large attachments constantly. OquMail's free plan gives each mailbox 5 GB, which for most small businesses is several years of everything. If a mailbox is filling up, it is almost always attachments, and the fix is to save those to shared storage and archive the message, not to delete the thread.

Mistakes that lose mail while "archiving"

• Running Outlook AutoArchive on an IMAP account without knowing where the .pst went. The mail is gone from the server and lives in a file nobody backs up.
• Archiving in one app while another app is set to "delete messages older than 30 days from the server". Check POP settings on old devices.
• Deleting a departed employee's mailbox before exporting it. Export first, then delete.
• Assuming Trash is an archive. Most hosts empty Trash automatically after a set number of days.

Common questions

Does archived mail still count against my quota?

Yes if it is in a server folder; no if you exported it to a local file and then removed it from the server. For most small businesses the quota is not a problem, so keep mail on the server where it is searchable from every device.

Can I archive a whole year in one go?

Yes. In webmail or a desktop app, search for a date range such as before 1 January of last year, select all results and move them. Do it in batches of a few thousand messages if the app or connection is slow.

How do I open an archive years later?

Mbox files open in Thunderbird via ImportExportTools NG, and .pst files open in Outlook via File, Open, Open Outlook Data File. Both formats have been stable for decades, so a file you save today will still be readable.