Knowledge base
February 01, 2026
Archive Mailbox Microsoft 365 – Prevent full mailboxes
You probably recognize it. You want to send an important e-mail and Outlook indicates that your mailbox is full. No more e-mails to send or receive. This often happens at times when you can’t afford it. During quotes, contract meetings or busy project weeks.
Microsoft is capitalizing on this. As of January 2026, Exchange Online automatically activates archiving as soon as a mailbox reaches 96 percent capacity. This prevents blocking, but only if an Archive Mailbox is set up.
In this article you will read what an Archive Mailbox is, why it will become crucial for Dutch organizations starting in 2026 and how to implement it smartly and manageably within Microsoft 365.
What is an Archive Mailbox in Microsoft 365?
An Archive Mailbox is additional storage within Exchange Online that automatically stores older e-mails. Users continue to work as usual in Outlook or Outlook Web. Archived emails remain searchable and accessible.
Important to know:
– The Archive Mailbox is not a separate mailbox
– Users hardly notice any difference in usage
– Storage automatically grows along with it
– Security and permissions remain intact
For Dutch companies, this is a practical way to keep mailbox growth under control without requiring employees to change the way they work.
What will change as of January 2026?
Microsoft is introducing automatic archiving at 96 percent mailbox capacity in Exchange Online. Once this limit is reached:
– Older emails are automatically moved to the Archive Mailbox
– The primary mailbox remains available for new emails
– Rules such as “Do Not Archive” remain in place
– Administrators retain full control over policies and exceptions
Without an Archive Mailbox, nothing happens. The mailbox still fills up and users get blocked. This is precisely why preparation is important.
Why this is relevant to Dutch organizations
Dutch organizations mail a lot. Quotations, contracts, healthcare records, project communications and compliance emails often remain for years.
Without archiving, this leads to:
– Productivity loss due to full mailboxes
– IT support tickets and employee frustration
– Unnecessary risks around retention periods
– Poorer grip on information management
With an Archive Mailbox, you better comply with internal retention policies and support AVG principles such as data minimization and manageability.
Implementing Archive Mailbox: here’s how we do it
At ALTA-ICT, we implement Archive Mailboxes as part of a broader Microsoft 365 management strategy.
Step 1: Analysis
We map mailbox growth, usage and retention policies. Not assumptions, but data.
Step 2: Determine policy
Together we determine what will be automatically archived and when. Tailored to your organization and sector.
Step 3: Technical setup
We activate and configure Archive Mailboxes in Exchange Online. Including exceptions and user groups.
Step 4: Monitoring and optimization
We monitor the effect. Fewer full mailboxes, fewer disruptions and predictable management.
Common mistakes
What we often see in organizations:
– Archive Mailbox not activated while storage is nearly full
– No clear retention periods
– Insufficient communication to users
– No monitoring on mailbox growth
This still leads to disruptions, despite the new Microsoft functionality.
ROI for SMEs
An Archive Mailbox costs hardly any additional license fees, but delivers immediate benefits:
– Fewer IT support moments
– No work stoppages due to full mailboxes
– Better control over data
– Higher employee satisfaction
For many SME organizations, this is a quick optimization with immediate effect.
Why ALTA-ICT
ALTA-ICT supports Dutch organizations daily with Microsoft 365 management and optimization.
You benefit from:
– ISO27001 and ISO9001 certified process
– Experience with Dutch SME environments
– Practical setup without unnecessary complexity
– Proactive management and advice
We ensure that new Microsoft changes do not become a surprise, but an advantage.
Frequently Asked Questions
- Should every user have an Archive Mailbox?
No, but without an Archive Mailbox, automatic archiving does not work. In practice, we recommend this for almost all users. - Can users still find their emails?
Yes. Archived emails remain fully searchable in Outlook. - Is this safe and compliant?
Yes. The Archive Mailbox falls under the same security and compliance settings of Microsoft 365.
Conclusion
As of January 2026, automatic archiving in Exchange Online will become a reality. Without Archive Mailbox, you run the risk of full mailboxes and work stoppages.
By setting up Archive Mailboxes now, you will avoid problems and keep a grip on e-mail management.
Want to know if your Microsoft 365 environment is ready for this? Schedule a free consultation with ALTA-ICT and avoid surprises.
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