Yes—both new Outlook for Windows and classic Outlook for Windows can attach ordinary files. The differences are in where you can select files from, which Outlook-specific items you can attach, and how you handle received files. Microsoft’s feature comparison, last updated September 23, 2026, lists network-share access as available in classic Outlook but not supported in new Outlook; Microsoft also says its new Outlook attachment workflow does not support attaching calendar information.
What differs between new Outlook and classic Outlook?
The comparison below is limited to Outlook for Windows. The available controls can also depend on account type, Microsoft 365 subscription, and organization policy.
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| Task | New Outlook for Windows | Classic Outlook for Windows |
|---|---|---|
| Attach an ordinary file | Use Attach File on the Message tab. Recent files may be suggested; where offered, choose a file attachment or a OneDrive link. | Use Attach File in the Message tab’s Include group. Recent items and the Attach Item option are documented. |
| Select a file from a network share | Not supported, according to Microsoft’s feature comparison. | Available, according to Microsoft’s feature comparison. |
| Attach a Business Card or Outlook item | No equivalent option is described in Microsoft’s new Outlook attach-file guidance. | Attach Item provides options for a Business Card or Outlook item. |
| Attach calendar information | Microsoft says calendar information is not supported in this attachment workflow. It suggests calendar sharing or a scheduling poll as alternatives. | Classic Outlook documents attaching an Outlook item. The cited guidance does not establish every calendar-attachment case. |
| Handle a received file | Preview, download, or save to OneDrive; downloading all attachments is also documented. | Use Save As, Save All Attachments, or drag and drop. Microsoft’s guidance names Documents as the default save folder. |
| Preview and edit | Preview is available for many file types. Office files can be edited in a browser or Office app; unsupported types must be downloaded and opened elsewhere. | Preview is available, with controls in Trust Center and possible additional support from installed previewers. Office files can be edited in a browser or desktop Office app; unsupported types must be downloaded. |
Microsoft’s September 23, 2026 feature comparison describes availability for Outlook for Microsoft 365. Do not assume each difference applies unchanged to Outlook on the web, Mac, mobile, every account type, or every organization’s configuration.
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How to attach a file in either Windows app
New Outlook
- Start a new message or reply, then open the Message tab.
- Select Attach File and choose a recent file or browse to one.
- If Outlook offers a OneDrive link or a traditional attachment, choose based on recipient access and whether you want to send a copy or share the cloud-stored file.
- Before sending a link, check that recipients have permission to open it. A link is not the same as an attached copy.
Classic Outlook
- Start a new message or reply, then open the Message tab.
- In the Include group, select Attach File and choose the file.
- To attach a Business Card or Outlook item, use Attach Item instead.
- If you share a SharePoint file, classic Outlook may warn that recipients might not have access and offer Attach as copy.
How to open, save, and edit received attachments
Previewing is not editing
Outlook can preview many common Office files, attached Outlook items, images, and text files, but support depends on the file type, installed application or previewer, and configuration. A preview lets you inspect a file; it does not mean Outlook can edit it. Classic Outlook’s preview controls are in Trust Center, and third-party previewers may support additional formats.
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Saving a file
In new Outlook, use the download or Save to OneDrive option; Microsoft also documents downloading all attachments. In classic Outlook, use Save As for one file or Save All Attachments for several, or drag an attachment to a folder. The destination you choose matters if you need to locate the file later.
Editing a file
Office files can be opened for editing in a browser or an Office app. For unsupported file types, download the attachment and open it in an application that supports that format. If the message contains a cloud-sharing link rather than a file copy, edits may affect the shared file; editing a downloaded copy does not by itself update that cloud file.
Why can’t I attach a file?
The file is on a network share
Microsoft’s feature comparison lists network-share file access as available in classic Outlook and unsupported in new Outlook. If the file is stored on a network location and new Outlook cannot select it, use an approved local or cloud location if your organization permits, or use classic Outlook for this workflow.
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Microsoft says Outlook blocks file types that could spread viruses, including some executable and script formats. This is a security control, not necessarily a fault with the app. Use an organization-approved cloud-sharing link when permitted, and follow workplace policy. Do not treat renaming a file or putting it in a ZIP archive as making a suspicious file safe or guaranteeing delivery.
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The message is too large
Microsoft’s support guidance gives a 20 MB limit for internet email accounts such as Outlook.com or Gmail, including the message and attachments. For Exchange business accounts, it gives a 10 MB default, also including the message and attachments. These are guidance figures, not universal guarantees: account, server, or tenant settings can differ.
For a file that exceeds the configured limit, Microsoft recommends a file-sharing service or compression. New Outlook guidance includes cloud links, compression, and SharePoint libraries in business settings; classic Outlook guidance also includes cloud links, compression, and automatic image-file resizing. Changing an inserted image’s display size in new Outlook does not reduce the underlying file size. A link still depends on recipient permissions, and neither compression nor a sharing link overrides server rules or organizational policy.
The attachment appears in the message body
In classic Outlook, this can happen when the message is in Rich Text Format (RTF). Microsoft says RTF attachments appear in the body, while plain-text attachments appear below the subject. Shared links are preserved as links only in HTML-formatted mail; in Rich Text or plain text, they may be added as a copy.
Which version should you use?
- Choose new Outlook for ordinary attachments, recent-file suggestions, and its documented OneDrive sharing workflow, provided the file source and account are supported.
- Choose classic Outlook when you need the documented network-share workflow or its Attach Item route for a Business Card or Outlook item.
- Use a sanctioned cloud link for a large or blocked file when policy permits and recipients can access it. Choose an attached copy when recipients need the file itself rather than access to a shared cloud item.
- Check with your administrator if an attachment is blocked or a size limit conflicts with business needs. Some Exchange settings may be adjustable, but local workarounds do not necessarily change server-side restrictions.
For attachments from unfamiliar senders, verify the sender and file before opening. Preview availability and file extensions do not establish that a file is safe.
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