Outlook on the web does not provide a general user setting to turn off blocked-attachment protection. You can preview, download, save, or edit supported files, but if Outlook blocks a file in a work or school account, contact your Microsoft 365 or Exchange administrator. For a legitimate file that cannot be attached, Microsoft recommends sharing it through OneDrive or SharePoint instead.
What you can and cannot change in Outlook on the web
Outlook blocks some potentially unsafe file types, including examples such as .exe, .bat, .vbs, and .js. Microsoft’s guidance does not document a personal Outlook on the web switch for disabling that protection. The available actions for supported attachments—such as opening or previewing, downloading, saving to OneDrive, or editing supported Office files—do not change whether a blocked file type is allowed.
Attachment blocking and attachment preview are different controls. Microsoft documents a “Turn off Attachment Preview” option for classic Outlook for Windows at File > Options > Trust Center > Trust Center Settings > Attachment Handling. That setting is not an Outlook on the web control and does not unblock a prohibited file type. See Microsoft’s blocked-attachment guidance and attachment workflow instructions.
If a file is blocked in a work or school account
Ask your Microsoft 365 or Exchange administrator whether the organization’s configuration permits an exception. Microsoft says an Exchange administrator may be able to unblock certain types or adjust mailbox security settings, but that does not mean every organization allows it. There is no universal user-facing menu path to change an organization’s policy. Microsoft explains this in its blocked attachments article.
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Use OneDrive or SharePoint to share a legitimate blocked file
- Ask the sender to upload the file to OneDrive or SharePoint rather than attach the blocked file to an email.
- Have the sender share a link with access limited to the intended recipients.
- Confirm an unexpected file with the sender through a trusted channel before opening it. A link is not proof that a file is safe.
Microsoft recommends sharing a OneDrive link for file types that Outlook blocks. See Microsoft’s blocked-attachment guidance. Avoid treating a renamed file extension as a safety fix: changing the displayed name does not make executable content harmless.
Settings that sound related but control something else
- Outlook.com advanced security: Eligible Microsoft 365 Personal or Family subscribers using personal Outlook.com mailboxes have separate advanced-security settings. The Safelinks control is at Settings > Subscription > Security. It affects link protection, not attachment blocking in an organization-managed Outlook on the web account. See Microsoft’s Outlook.com advanced-security information.
- Link Preview: The setting at Settings > Mail > Compose > Link preview controls rich previews of URLs in messages, not attachment scanning or blocking. See Microsoft’s Link Preview instructions.
- External images: Microsoft’s cited instructions for blocking external images are specific to mobile and concern remote images and privacy, not a web attachment-safety setting. See Microsoft’s mobile guidance.
Do not confuse current Outlook on the web with older Outlook Web App guidance
Microsoft also has older Outlook Web App instructions for Exchange Server 2013 and 2010. Those legacy directions are not a current settings path for Microsoft 365 Outlook on the web. They advise using preview rather than downloading attachments on a shared or public computer, and signing out when finished. For a message Outlook marks as potentially unsafe, Microsoft’s Outlook.com guidance advises not opening it. See legacy Outlook Web App security guidance and Outlook.com account-protection guidance.
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