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Fix Cannot Send Email from an Alias in Outlook on the Web
Question details
The user is unable to send emails using an Exchange Online alias via Outlook on the web, even though the same alias works fine in the Outlook desktop application.
- Product
- Outlook on the Web
- Device & OS
- not provided
- Scenario
- Attempting to compose and send an outgoing message using a configured email alias via the web version of Outlook.
- Observed behavior
- The email fails to send because the alias is not properly enabled in the web settings, or a cached and incorrect autocomplete address is being used.
Ensure that your Microsoft 365 administrator has correctly added the alias to your Exchange Online account and allowed sufficient time (up to 24 hours) for the server changes to propagate.
Enable the Alias in Compose and Reply Settings
Outlook on the web requires you to manually select which aliases you are permitted to send from before they can be used in the 'From' field.
By default, newly added aliases might not be visible in your sending options on the web until they are explicitly enabled in the settings menu.
Log in to Outlook on the web and click the Settings (gear) icon in the top right corner of the screen.
Go to 'Mail' in the left sidebar, then select 'Compose and reply'.
Scroll down to the 'Addresses to send from' section and check the box next to the alias you want to use.
Save your settings. You should now be able to select this alias from the 'From' dropdown when composing a new message.
Manually Type the Alias to Bypass Autocomplete Cache
Cached autocomplete entries can cause send failures if your browser is automatically inserting an outdated or improperly formatted address.
Clear Browser Cache or Use Incognito Mode
Stale browser cache can prevent Outlook on the web from recognizing updated Exchange settings or newly added aliases.
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Frequently Asked Questions
Why does my email alias work in the Outlook desktop app but not on the web?
Outlook on the web often requires you to manually select which aliases are allowed for sending within its specific settings menu (Mail > Compose and reply). The desktop client syncs and handles these permissions differently directly from Exchange.
How long does it take for a newly created alias to show up in Outlook on the web?
It can take up to 24 hours for a new Exchange Online alias to fully sync across Microsoft 365 servers and become available in your Outlook on the web settings.
Can I make my alias the default sending address in Outlook on the web?
Yes. You can set the default 'From' address by going to Settings > Mail > Compose and reply, and selecting your preferred alias under the 'Set default From address' dropdown menu.
