How to Fix Hotmail Delivery Failures in Outlook
Question details
Users are experiencing delivery failures with a mailbox-unavailable error when attempting to send emails to Hotmail or Outlook.com addresses from Outlook.
- Product
- Microsoft Outlook
- Device & OS
- not provided
- Scenario
- Sending an email to a Hotmail or Outlook.com recipient.
- Observed behavior
- The email fails to deliver, and a bounce-back message (nondelivery report) is returned stating that the mailbox is unavailable.
Verify that your internet connection is stable and ensure you have the exact, correct spelling of the recipient's email address.
Clear the Autocomplete Entry and Enter the Address Manually
Removing a potentially corrupted or outdated autocomplete suggestion forces Outlook to use the correct routing information for the email address.
A common cause of the mailbox-unavailable error is a stale autocomplete entry in Outlook's cache. Even if the address appears correct visually, the underlying cached routing data might be outdated.
Launch Microsoft Outlook and click on 'New Email' to open a blank message window.
Begin typing the recipient's Hotmail or Outlook.com address in the 'To' field. When the autocomplete suggestion drops down, click the 'X' icon next to the name to delete it from the cache.
Carefully type the entire email address manually, or click the 'To' button to select the recipient directly from your Contacts list.
Send the newly addressed message to verify if the delivery failure has been resolved.
Review the Nondelivery Report (NDR)
If sending the email manually still fails, the detailed error report will help identify server-side or recipient-side issues.
Looking for a Lightweight Alternative to Microsoft Office?
While resolving Outlook delivery issues, consider streamlining your document management with WPS Office. It is a completely free, highly compatible alternative to Microsoft Word, Excel, and PowerPoint.
- 1. Download the software: Visit the WPS Office website and click the download button for your operating system.
- 2. Install WPS Office: Run the setup file and follow the on-screen instructions to install the suite.
- 3. Open your files: Launch WPS Office and immediately open, edit, and save your existing Office documents.
Frequently Asked Questions
Why am I getting a mailbox-unavailable error if the email address is spelled perfectly?
Even if the spelling is correct, Outlook might be using a corrupted background link from its autocomplete cache. Additionally, the recipient's mailbox might be temporarily suspended, permanently deleted, or full on the server side.
Will adding the recipient to my Contacts list prevent delivery failures?
Yes, saving the correct, verified email address to your Outlook Contacts list and selecting it from the Address Book helps prevent issues caused by typos or outdated cache entries.
Does a delivery failure mean my internet is disconnected?
No. A nondelivery report (bounce-back) actually confirms that your email successfully left your outbox and reached the outgoing server, but was rejected by the recipient's incoming server.
