In short
Office 365 email archiving can mean Microsoft's own tools (archive mailboxes, Purview retention policies, eDiscovery and holds) or a separate archive that receives a journaled copy of every message. Native tools keep data in place inside your tenant. A journaling archive such as NinjaOne Archiver keeps an independent copy outside it, with legal hold and backup, including leavers' mail.
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Microsoft's built-in archiving and retention
Microsoft 365 (still widely called Office 365) gives you several features that people loosely call "archiving". They do different jobs, and it helps to separate them before comparing anything else.
| Feature | What it does | What to know |
|---|---|---|
| Archive mailbox | Adds up to 100 GB of extra mailbox storage; users or archive policies move older mail into it | Mainly a storage feature. Users still see and manage the mail. See Exchange Online Archiving |
| Auto-expanding archiving | Grows the archive mailbox automatically, up to 1.5 TB | Microsoft is raising the cap to 3 TB for eligible E5-type licences, with rollout from mid-October 2026 |
| Exchange Online Archiving add-on | Adds an archive mailbox, auto-expanding archiving and Litigation Hold to plans that lack them | Licensed per user; one archive per licensed user |
| Microsoft 365 retention policies and labels | Keep or delete content in place across Exchange, SharePoint, OneDrive and Teams | Microsoft's recommended approach for retention |
| Microsoft Purview eDiscovery | Search, hold, review and export content across workloads | The classic Content Search and eDiscovery experiences were retired on 31 August 2025 |
| Litigation Hold | Preserves a whole mailbox, including deleted items | Still supported, but Microsoft now favours retention policies and eDiscovery holds |
| Inactive mailboxes | Keeps a leaver's mailbox after the account is deleted | Only if a hold or retention policy was applied before deletion; otherwise data goes after 30 days |
Which of these you already have depends on your plan. Some plans include archiving and others need the add-on; Forever Group's Microsoft licensing team can check what your subscriptions include.
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Where Microsoft's native tools fit well
It is worth being fair about this. Microsoft's own documentation on journaling says that, "when possible", it recommends using Microsoft 365 retention to archive and manage data in place. Native retention has real strengths:
- Nothing extra to buy if your plan already includes the features you need
- More than email: one set of retention policies can cover Exchange, SharePoint, OneDrive and Teams
- Data stays in your tenant, so there is no second copy to secure or deduplicate
- Mature eDiscovery in Microsoft Purview, with holds, review sets and exports on higher plans
If you have Microsoft 365 E3 or E5, a clear retention schedule and people who know Purview well, native retention may be all you need. We will say so if that is what we find. Our Cloud Security site covers Microsoft Purview in more depth.
Why organisations still add a separate journaling archive
Plenty of organisations look at the native tools and still decide they want an independent email archive. The usual reasons are practical rather than technical:
- Independence from the tenant: an archive held outside Microsoft 365 is not affected by a retention policy set up wrongly, an admin account that has been taken over, or a mailbox deleted before anyone applied a hold.
- Capture by journaling: Exchange Online sends a copy of each message to the archive as it passes through, so the record does not depend on what users keep. Read more on Exchange Online journaling.
- Tamper-resistant record: NinjaOne describes Archiver as immutable email archiving with full audit trails, and a stricter write-once (WORM) setting can be switched on for Archiver accounts. WORM cannot be undone and changes how retention and roles work, so it is a decision for scoping.
- Separate compliance roles: NinjaOne's Compliance and Review Officer, Data Protection Officer and Reviewer roles give compliance, HR or legal staff their own access, and its IT Admin role has no access to the compliance tab.
- Leavers without licences: archived mail stays searchable after the account has gone, with NinjaOne's deactivated-seat allowance confirmed when we quote. See former employee mailboxes.
- Archive and backup in one console: the Archiver bundles include NinjaOne SaaS Backup Standard for mailboxes, OneDrive, SharePoint and Teams channels.
Microsoft is open about the trade-off: journaling moves data outside Microsoft 365, so the receiving archive must be secured, and it is the customer's job to watch for undelivered journal reports. That is one reason to choose a managed, cloud-native archive and have someone check the set-up properly.
Is Office 365 email archiving the right fit for you?
We will check it against your systems and requirements and recommend the right option.
Native tools vs NinjaOne Archiver at a glance
A side-by-side summary. The detail varies by Microsoft plan and by the NinjaOne bundle you choose.
| Question | Microsoft 365 native | NinjaOne Archiver |
|---|---|---|
| How is mail captured? | Kept in place in the mailbox, subject to retention policies | Real-time journaling of inbound and outbound mail at server level |
| Where does the data sit? | Inside your Microsoft 365 tenant | In NinjaOne's cloud, outside your tenant; we confirm the location before set-up |
| Can users delete it? | They can delete from their view; retention keeps a copy in hidden folders | No. The journaled copy sits in the archive, separate from the mailbox; an optional WORM setting locks it further |
| Retention | Retention policies and labels by location, group or label | Policies by user, department or domain, from 30 days to indefinite |
| Search and review | Microsoft Purview eDiscovery | eDiscovery with saved searches, tags and alerts, and reviewer roles |
| Legal hold | eDiscovery holds, retention, Litigation Hold | Legal hold that freezes retention for held data until removed |
| Leavers | Inactive mailbox if a hold or retention policy applied first | Archived mail stays available after the account goes |
| Teams | Retention and eDiscovery for chats and channel messages | Channels in SaaS Backup; private chats with the Archiver plan |
| Backup | Microsoft 365 Backup is a separate pay-as-you-go service | SaaS Backup Standard included in the Archiver bundles |
For the full bundle comparison see NinjaOne SaaS Backup Standard vs Archiver bundles, and for the product itself see NinjaOne Archiver. For backup on its own, our Cloud Security site explains Microsoft 365 backup.
How NinjaOne Archiver archives Microsoft 365 mail
Set-up for Microsoft 365 is largely automated. In outline, from NinjaOne's documentation:
- You authenticate your Microsoft 365 tenant in the NinjaOne SaaS Backup console.
- NinjaOne connects over remote PowerShell and creates a journal rule and a distribution group in Exchange Online. The journal reports go to a dedicated external journal mailbox for your organisation, on mail servers NinjaOne manages.
- Mailboxes you add to the archive become members of that group, so their mail is journaled from then on.
- Mail already in those mailboxes is captured by the initial backup, so the archive starts with history rather than an empty store.
- Retention policies, Department Sync and reviewer roles are then set to match your retention policy.
NinjaOne is candid that it "cannot guarantee a 100% success rate" for journaling, and that journal errors are usually credential problems fixed by reauthenticating. That is why we can check, as part of set-up, that journal reports are arriving. The full process is on how NinjaOne Archiver is set up, and chat archiving is covered on Teams chat archiving.
Native, separate, or both?
It is rarely a straight choice. Many organisations use Microsoft 365 retention for SharePoint, OneDrive and Teams, and add a journaling archive for email because mail is where most disputes, complaints and requests for information start. Some questions that usually settle it:
- Does your plan already include archiving and the eDiscovery tier you need, or would you be buying add-ons anyway?
- Do you need a copy of mail held outside your tenant, for example to satisfy a regulator's expectation of a durable record? See FCA email retention.
- How do you handle leavers today, and are you paying for licences just to keep their mail?
- Who runs searches: IT, or compliance, HR and legal staff who need their own controlled access?
- Do you also need backup that can restore mailboxes, OneDrive and SharePoint?
If you are writing or reviewing the rules first, start with our email retention policy guide.
How Forever Systems helps
We supply NinjaOne SaaS Backup with Archiver for Microsoft 365 and help you set it up to match your policy. We start by looking at what your Microsoft plans already give you, so you only add what you need. Then we can:
- Recommend the right bundle and seat count, and confirm the term, the storage allowance tied to paid seats and how leavers count towards seats in the quote
- Confirm where your archive will be held before set-up
- Help authenticate the tenant and check journal reports are flowing
- Set retention policies by department, user or domain, and assign compliance and reviewer roles
- Plan the move of any legacy archive or PST files through NinjaOne's ingestion service; see email archive migration
Microsoft licences themselves are handled by Forever Group's Microsoft 365 team. For the archive, ask us for a quote: Contact us.
Microsoft 365 archiving guides
How Forever Systems helps with email archiving
We are an independent UK IT and cyber security provider. We supply NinjaOne SaaS Backup with Archiver for organisations on Microsoft 365 or Google Workspace, and help you get the archive set up, the policies right and the people who need it confident using it.
- Scoping: we look at your mailboxes, leavers, legacy archives and record-keeping obligations, and what your Microsoft 365 or Google Workspace plan already includes, before suggesting anything new
- Set-up: we can configure journaling for Exchange Online or Google Workspace, connect the archive and check that mail is arriving
- Retention and legal hold: we help you turn your email retention policy into archive rules, and show your compliance or HR lead how to search, hold and export
- Leavers and legacy archives: we can help you plan how former employees' mail and older archives are brought across, with the approach confirmed at quote
- Backup alongside the archive: the same NinjaOne per-user licence also covers backup of your Microsoft 365 or Google Workspace data, so recovery and record-keeping are planned together
We work with businesses, schools, charities and public sector organisations. If you also need wider protection, see our independent cloud security guides.
Frequently asked questions
Does Office 365 have email archiving?
Yes. Microsoft 365 includes archive mailboxes (on many plans), auto-expanding archiving, retention policies, eDiscovery and holds, and the Exchange Online Archiving add-on brings archiving to plans without it. These keep data inside your tenant. A separate journaling archive keeps an independent copy of every message outside it.
Is the Outlook Archive folder the same as email archiving?
No. Outlook's Archive button just moves a message out of the inbox into an Archive folder in the same mailbox, where the user can still delete it. A compliance archive captures every message as it is sent or received and keeps it unaltered for a set period. See what is email archiving?
Do I need a third-party archive if I have Microsoft 365 E3 or E5?
Not necessarily. Microsoft recommends its own retention where possible, and E3 and E5 include strong features. Organisations add a separate archive when they want a copy outside the tenant, journaling capture, compliance roles separate from IT, simpler handling of leavers, or backup in the same licence.
Can I keep a leaver's email without keeping their Microsoft 365 licence?
In Microsoft 365, a deleted user's mailbox only becomes an inactive mailbox if a hold or retention policy was applied before deletion; otherwise it is removed after 30 days. With NinjaOne Archiver, archived mail stays searchable after the account goes, within NinjaOne's deactivated-seat allowance, which we confirm when we quote.
Can Exchange Online journal to an Exchange Online mailbox?
No. Microsoft says you can't designate an Exchange Online mailbox as a journaling mailbox. Journal reports must go to an on-premises archiving system or a third-party archiving service, which is what NinjaOne Archiver provides.
How much does Office 365 email archiving cost?
Microsoft's own features depend on your plan, which Forever Group's Microsoft licensing team can check. For NinjaOne Archiver, the price depends on the bundle, the number of users and the term, so ask us for a quote.
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