Outlook Attachments Not Showing or Not Opening? Fixes

TL;DR: Most missing Outlook attachments are a blocked file type, a Rich Text message (attachments move into the body or arrive as winmail.dat), a reply (Outlook drops attachments on Reply by design), or Cached Exchange Mode keeping older mail on the server. Files that will not open are usually Protected View, a mismatched previewer, or a double-click that is too fast. Every fix below links to the Microsoft page it comes from.

Disclosure: The Drive AI publishes this guide. It files email attachments into folders; it does not fix Outlook. The Outlook behaviour below comes from Microsoft's support and Learn pages as of November 2026, linked at each fix. Where Microsoft documents no fix, none is given.

Why are attachments not showing in Outlook?

An attachment the sender swears they attached is usually blocked, inside the message body, or a OneDrive link rather than a file. Check these in order.

1. A blocked file type. Outlook blocks the sending and receiving of a long list of file extensions, including .exe, .bat, .cmd, .js, .msi, .ps1, .reg, .vbs, .iso, .lnk, .url and .pst. In Outlook on the web the message shows a placeholder such as "1 Attachment" that cannot be opened, or "Access to attachments has been blocked"; an administrator can change the Outlook on the web mailbox policy, and the workaround for everyone else is to zip the file. Microsoft's other suggestions: rename the extension (and restore it after receipt), or share the file from OneDrive or SharePoint as a link.
2. The message is in Rich Text format. In classic Outlook, "if you RTF, any files you attach will show up in the message body", not under the subject line. Switch the format to HTML or Plain Text (Troubleshoot attachment problems in Outlook for Windows).
3. It is a link, not a file. When a OneDrive or SharePoint file is shared from Outlook desktop, the link is now inserted inline in the message body with the file's icon and name, not as a cloud attachment. Look in the body. The sender can instead choose to attach a copy, which "gives each recipient an identical personal copy" (Attach files in Outlook).
4. The sender's Outlook used TNEF. If you received winmail.dat instead of the files, see the winmail.dat section below. Microsoft lists "recipient doesn't receive regular file attachments" as a TNEF symptom.

Why do attachments disappear when I reply?

Because Outlook removes them on purpose. Microsoft's page on replying in classic Outlook says, under both Reply and Reply All, "Attachments are not included", and adds: "There is no way to change this behavior" (Reply to or forward an email message).

The attachments are still on the original message in the thread; only your reply lacks them. If you need them to travel, use Forward: "any attachments included in the original message are automatically included when you forward a message." Or reply and attach the file again by hand.

Why won't an attachment open in Outlook?

If the file is listed but will not open, the documented causes are Protected View, a missed double-click, a blocked type, or a PDF handed to Edge.

1. Protected View is holding it read-only. Office opens attachments from senders your policy marks unsafe in Protected View. Select Enable Editing on the yellow bar; on a red bar, select File > Edit Anyway. The setting lives under File > Options > Trust Center > Trust Center Settings > Protected View, and an administrator can lock it (What is Protected View?).
2. Double-clicking does nothing. Microsoft's documented cause, for Outlook 2016 onward, is a mouse double-click speed set too fast. Right-click the attachment and select Open, or slow the slider under Control Panel > Mouse > Buttons (Cannot open attachments by double-clicking).
3. It is a blocked type. Outlook blocks receiving the file, so there is nothing to open. Ask the sender to zip it or share a link.
4. A PDF opens in Edge. In new Outlook, PDFs open in Edge when it is the default browser; change the default app for .pdf in Windows to use another viewer (Troubleshoot attachment problems).

Why does the attachment preview fail?

Preview in classic Outlook "only works if you have the same version of Word, Excel, or PowerPoint installed" as Outlook, and the four apps must share the same user interface setting (Optimize for best appearance or Optimize for compatibility). Attachments inside the message body cannot be previewed at all (Preview attachments in Outlook). Two more documented causes:

1. Preview is switched off. Check File > Options > Trust Center > Trust Center Settings > Attachment Handling. "Turn off Attachment Preview" disables all previewers; "Attachment and Document Previewers" disables them one at a time.
2. "This file cannot be previewed because there is no previewer installed for it" on a PDF. Microsoft's known-issue page gives two causes: Adobe Acrobat Reader is not the same bitness (32 or 64) as Outlook, or Microsoft PowerToys has taken over PDF preview. Reinstall Reader in the matching bitness, or turn off "Enable PDF (.pdf) preview" under PowerToys > File Explorer Add-ons (Outlook PDF preview error).

What is winmail.dat and why did my recipient get it?

winmail.dat is Outlook's Rich Text packaging (TNEF), which only Exchange-based mail systems understand. When the recipient's system cannot read it, "a file attachment that's named Winmail.dat is added to the message", and the real attachments may be trapped inside it (How message format affects email messages).

1. Fix it for all mail. In Outlook, File > Options > Mail > Compose messages in this format, choose HTML or Plain Text.
2. Fix it for one message. On the Format Text tab, select Message Format and pick HTML or Plain Text.
3. Fix it for a whole company. A Microsoft 365 admin can set Set-RemoteDomain -Identity <Name of Domain> -TNEFEnabled $false for an external domain, or -UseMapiRichTextFormat Never on a mail contact (Specify the message format for external recipients).

Voting buttons, meeting requests and task requests still need Rich Text; turn it on per message for those.

Why are attachments not loading or not downloading?

In classic Outlook with Cached Exchange Mode, mail older than the sync window is not on your computer. The "Mail to keep offline" setting (renamed "Download email for the past" in later versions) defaults to 1, 3 or 12 months depending on disk size, and items outside it "reside only in your mailbox on the server". A folder then shows "There are more items in this folder on the server. Click here to view more on Microsoft Exchange" (Only a subset of your Exchange mailbox items is synchronized).

1. Widen the window. File > Account Settings > Account Settings, double-click the Exchange account, drag the slider to All, then restart Outlook.
2. Know where downloads go. New Outlook saves to Documents, a default that cannot be changed; use the attachment's drop-down and Save As for another folder. A duplicate name gets a number appended, not an overwrite prompt (Troubleshoot attachment problems).
3. Use the right command per client. Classic Outlook has Save All Attachments, new Outlook has Download all, and Outlook on the web offers Download, Save to OneDrive or Download all (Open or save attachments); the steps are in the guide to download all attachments from Outlook.

Why did my attachment fail to upload or send?

Size or type. Exchange Online's default message size limit is 35 MB to send and 36 MB to receive, adjustable by an admin from 1 MB to 150 MB. A classic attachment in Outlook on the web can be up to 112 MB, a OneDrive attachment up to 2 GB, and a message can carry 250 attachments (Exchange Online limits). Over the limit, send a OneDrive link instead; in new Outlook, "Share link saves the file to OneDrive (if it isn't already)". A blocked type is refused at any size; zip it first. Microsoft publishes no page for the generic "failed to upload" message beyond these causes, so nothing else is claimed here.

How do new Outlook and classic Outlook differ on attachments?

The commands are named differently, and several settings exist only in classic.

The cause behind most of these searches

Every fix above has the same shape: the file is inside a mailbox, so whether you can see it depends on the sender's format, your client, a sync window and a trust setting. A file in a folder has none of those conditions. It opens like any other file, for anyone with access to the folder.

The native route is to save attachments out by hand, or to find emails with attachments and download them in batches. The alternative is a workflow that files them as they arrive. In The Drive AI (Max or any Team plan), an Email Attachment workflow saves a copy of each attachment into The Drive AI or a connected OneDrive, SharePoint, Google Drive or Dropbox folder, reads it, and names and files it by what it says. The email is never changed. Limits worth knowing: Outlook here means mailboxes hosted by Microsoft, on-premises Exchange is not supported, and a workflow watches the account that receives the mail. The setup is in the guide to automatically save Outlook attachments, the wider options are compared in the email attachment management software roundup, and the overview of how to organize email attachments automatically covers both Gmail and Outlook.

Frequently Asked Questions

Can I make Outlook keep attachments when I reply?

No. Microsoft's reply page says there is no way to change this. Forward the message instead, or re-attach the file.

Why can my colleague open an attachment that I cannot?

Try Outlook on the web. If it opens there, the cause is local to your desktop: Protected View, the previewer, or Cached Exchange Mode.

Why does Outlook block an attachment as unsafe?

Its extension is on the blocked list. Zipped copies pass because the extension changes, and an Exchange administrator can unblock a type for the organisation.

Where did Outlook save my downloaded attachment?

New Outlook saves to Documents by default. Classic Outlook asks each time. If you cannot find an older file, the guide on how to find old email attachments covers the usual places.

Does deleting attachments free up mailbox space?

Yes, if you delete or save-and-remove the attachments; see how to delete large email attachments without losing the files.

Try it on your files

If the same attachments keep going missing, file them once and stop depending on the mailbox. Create a free account and try the instruction below on a sample folder, or connect a mailbox on Max or any Team plan to save Outlook attachments as they arrive.