A mailbox warning arrives while your team is exchanging estimates, invoices and project approvals. The tempting response is to delete the oldest messages until the warning disappears. Those messages may also explain what a customer approved or why a bill changed.
For a Bay Area business using Microsoft 365, the first job is to establish which limit applies and which records must stay. That can reveal an available storage entitlement before anyone removes useful correspondence.
Identify the mailbox and its actual quota
Confirm with IT that the affected account is hosted in Exchange Online. Using the Outlook app alone does not establish the email service or license. Personal Outlook.com accounts and other providers need their own storage guidance.
In Outlook on the web, open Settings > Account > Storage to inspect mailbox usage and the largest folders. New Outlook uses Settings > Accounts > Storage. Microsoft documents these views in its work-account storage guide. Look first; leave permanent-deletion controls alone.
Ask your administrator to record the assigned license, enabled services, current usage and configured warning, send and receive quotas. A subscription's maximum allowance and a mailbox's configured limit can differ. Microsoft allows administrators to set lower mailbox quotas.
Check the 2026 Business-suite storage change
Microsoft's August 2026 Exchange Team guidance describes a maximum 100 GB primary-mailbox entitlement for eligible Microsoft 365 Business Basic, Standard and Premium users. The Business Exchange service and additional 50 GB storage service plan must both be enabled. Existing custom quotas are preserved.
Standalone Exchange Online Plan 1 still has a 50 GB limit; Plan 2 provides 100 GB. Consult the current Exchange Online limits for the exact plan and mailbox type.
If a Business-suite mailbox still shows a lower quota, have IT check provisioning and custom settings before buying an upgrade. Microsoft specifically warns against removing and reassigning an Exchange license just to force a quota refresh unless Microsoft Support directs it.
Understand the warning's urgency
Exchange Online distinguishes three stages:
- Warning: the mailbox is approaching its configured limit.
- Prohibit send: the mailbox cannot send new messages.
- Prohibit send/receive: it cannot send or receive; incoming messages are rejected, and the sender receives a non-delivery report.
The mailbox usage report exposes these quotas, but its data typically lags by 24 to 48 hours. For an active interruption, ask IT to check current mailbox conditions rather than relying only on that report. Once receiving works again, ask affected senders to resend rejected messages.
Choose the right kind of archive
The ordinary Archive folder remains inside the mailbox. Clicking Outlook's Archive button organizes messages but does not reduce mailbox size.
An Online Archive, also called In-Place Archive in some Outlook versions, is a separate mailbox location where older mail does not consume primary-mailbox space. An administrator enables it and manages the applicable policies. Microsoft explains the distinction in its Online Archive guide.
Have IT verify archive eligibility, capacity and the move policy before changing anything. The Business-suite primary-storage increase does not itself add archive capabilities. Test that staff can find an approved sample of moved correspondence before relying on the archive for daily work.
Preserve records before cleanup
Separate material approved for disposal from records the business still needs. Age alone is a poor deletion rule for contracts, project approvals or unresolved disputes.
Have the person responsible for records confirm retention requirements and any legal hold before cleanup. Where legal obligations are unclear, obtain appropriate legal advice. Do not disable a hold or shorten retention to make a storage warning disappear.
Under applicable retention settings, deleted messages may remain in Recoverable Items. Microsoft's Exchange retention guidance explains how preservation can continue after a message leaves the visible folder. Ask IT to investigate unexpected storage behavior rather than repeatedly purging mail.
A checklist for the support request
- Capture the warning, affected address, time and business impact.
- Confirm the account type, license, enabled storage services and actual quotas.
- Review large folders without bulk-deleting their contents.
- Agree what must be retained and what may be removed.
- Select an approved archive, quota correction or licensing change with IT.
- Recheck usage and sending/receiving after the change; assign a follow-up review.
VFIX's help desk service provides remote troubleshooting through managed IT plans. Bring the warning and mailbox details to the support conversation so the next step addresses the actual limit while respecting the records your business needs.