How much space does a mailbox have in Microsoft 365?

In Microsoft 365 Business Basic, Standard and Premium a mailbox has 50 GB. The online archive comes on top of that: 50 GB with Business Basic and Standard, and growing automatically up to 1.5 TB with Business Premium.

Can email in the archive still be found?

Yes. The archive appears as an extra folder in Outlook and Outlook on the web. Employees can search it and open email as usual. Only in the classic Outlook app is the archive not available offline.

Is the online archive the same as a backup?

No. The archive sits in the same Microsoft 365 environment as the mailbox, so it can also be deleted by accident or by an attacker. A separate backup is still needed.

Why not use PST files?

PST files sit separately on a laptop or network drive. They get lost when a laptop is replaced, are often not included in the backup and cannot be searched by the organisation. The online archive does not have those drawbacks.

Mailbox full: how an SME should use the online archive in Microsoft 365

It starts with a yellow bar in Outlook: your mailbox is almost full. Employees then delete a few attachments, drag email into a PST file on their laptop or ignore the warning. Until the mailbox really is full and customers get their email bounced. For most SMEs there is a better solution that is already included in their plan: the online archive in Exchange Online.

What happens when a mailbox fills up

Microsoft warns well before a mailbox is full. If the limit is reached anyway, the employee first can no longer send email and then can no longer receive it either. Customers and suppliers get an error message back. You usually only notice when someone calls to say their quote never arrived.

Full mailboxes are most common for employees who keep everything, for mailboxes with lots of attachments such as drawings or scans, and for shared mailboxes such as info@ or invoices@ that have been in use for years.

The online archive: extra space already included in your plan

The online archive is a second mailbox that belongs to the employee’s mailbox. In Outlook it appears as an extra folder, usually called “Online Archive”. The employee can search it and open email as usual. The difference: the archive does not count towards the 50 GB of the regular mailbox.

Business Basic and Standard: a 50 GB archive per user.
Business Premium: an archive that grows automatically up to 1.5 TB. Also see which Microsoft 365 plan suits your business.
Shared mailboxes: without a licence they have 50 GB and no archive. An archive on a shared mailbox does require a licence.

How to put the archive to work

First check how full the mailboxes are. The admin center shows how much space each mailbox uses. Start with the mailboxes above 40 GB.
Switch on the archive per user. You do this in the Exchange admin center. The archive is then available straight away in Outlook and Outlook on the web.
Have old email moved automatically. By default, Exchange Online moves email older than two years to the archive once the archive is switched on. You can change that period, for example to one year for mailboxes that fill up quickly. The moving happens in the background and can take a few days the first time.
Bring PST files back into the cloud. If employees still have PST files on their laptop or a network drive, import them into the archive. After that they can be removed.
Explain what changes. Tell employees that old email is not gone, but sits in the archive, and that they can simply search it.

What to watch out for

In the classic Outlook app on the laptop, the archive is not stored offline. Without an internet connection, the employee cannot open it. For most people that is not a problem, because it concerns old email.

An archive is not a backup either. Email in the archive sits in the same Microsoft 365 environment and can just as easily be deleted by accident or by an attacker. Read why the cloud is not a backup. If you want to keep email for a fixed period, for example for tax record-keeping, retention policies are the right tool. The archive gives space; a retention policy decides how long something is kept.

How Floor ICT handles this

Floor ICT checks how full the mailboxes are for every client and switches on the online archive for employees and shared mailboxes that need it. We set a period for moving old email automatically, bring loose PST files back into the cloud and make sure mailbox and archive are included in the backup. Under our management we get an alert before a mailbox fills up, so your customers never get an error message back.

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