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How to Fix STOREDRV.Deliver Error: Recipient Mailbox Is Busy
Question details
The user is encountering a STOREDRV.Deliver timeout error indicating that the recipient mailbox is busy, which prevents successful email delivery.
- Product
- Exchange Online
- Device & OS
- not provided
- Scenario
- Sending an email to a recipient within or outside the organization.
- Observed behavior
- The email fails to deliver, and the sender receives a non-delivery report (NDR) or error message stating 'STOREDRV.Deliver' and 'Recipient Mailbox Is Busy'.
Confirm with your IT administrator whether there is a known Exchange Online service degradation before attempting to adjust any mail flow settings.
Wait and Check Microsoft 365 Service Health
Because this error usually points to a temporary backend processing issue, simply waiting and checking the service status is the most effective first step.
The 'STOREDRV.Deliver' error typically happens when the Microsoft Exchange Online server is temporarily overloaded or experiencing mail-flow processing delays.
Wait for 15 to 30 minutes, then attempt to resend the email to the recipient.
If you are an administrator, log into the Microsoft 365 admin center and navigate to Health > Service health to check for any ongoing Exchange Online advisories.
Run Admin Diagnostics and Message Trace
If the error persists for an extended period, an administrator must review the mail flow and trace the stuck messages.
Switch to a Lightweight and Reliable Office Suite
While waiting for Microsoft 365 email delivery issues to be resolved by your administrator, you can continue your document creation and data analysis without interruption using WPS Office. It is a free, fast, and highly compatible alternative that seamlessly handles all your standard Office files.
- 1. Download WPS Office: Visit the official WPS website to download the free installer for your operating system.
- 2. Install the Software: Run the installer and follow the quick setup wizard to complete the installation.
- 3. Open Your Documents: Easily open your existing Microsoft Word, Excel, and PowerPoint files and resume your work instantly.
Frequently Asked Questions
What does 'STOREDRV.Deliver' mean in an email bounce back?
STOREDRV is a core Exchange transport component that is responsible for delivering messages to a mailbox database. When it fails, it means the server successfully received the message but encountered a problem saving it into the specific recipient's mailbox.
Can I fix the 'Recipient Mailbox Is Busy' error as a standard user?
Standard users cannot directly fix this issue as it is typically a server-side problem. Your best option is to wait a few minutes and try resending the email. If it continues to fail, you should contact your IT department.
Why does Exchange Online temporarily stop processing messages?
This issue can happen due to routine background maintenance, unexpected service degradation on Microsoft's end, or if the recipient's mailbox is locked by another heavy process, such as a large mailbox migration or an automated archiving task.
