Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsIf Outlook blocks an attachment, Microsoft’s preferred workaround is to upload it to OneDrive or a secure SharePoint location and email the recipient a sharing link. You can also try sending a ZIP archive. Renaming a file extension is another documented workaround, but it only changes the filename—it does not make the file safe.
Why Outlook blocks some attachments
Outlook blocks certain file types to help protect senders and recipients from computer viruses. The exact steps and controls vary by Outlook version, so use the instructions for your client. Microsoft’s guidance covers several desktop, mobile, web, and Outlook.com versions, while its Windows troubleshooting page distinguishes new Outlook from classic Outlook.
As an Amazon Associate I earn from qualifying purchases.
See Microsoft’s blocked attachments guidance and its list and troubleshooting guidance for blocked file types.
Best method: share the file from OneDrive or SharePoint
Upload the file to OneDrive or an appropriately secured SharePoint location, then send a link. Microsoft describes this as the simplest way to send a blocked file. Set the link permissions so the intended recipient can open it, while granting only the access they need.
#1 Best Overall
- Certified to FIPS 197 - High-level information security standard approved by the U.S. Government
- Brute-Force Password Attack Protection - Data is automatically erased after 6 failed access attempts. The data and encryption key are securely destroyed and the crypto drive is reset
- Rugged Double-Layer Waterproof* Design - Protects the crypto drive against knocks, drops, break-in and submerging in water. The electronics are shielded by a hardended inner case. The rubberised silicone outer casing provides a final layer of protection
- Auto-lock - The crypto drive will automatically encrypt all data and lock when removed from a PC/Mac or when the screen saver or "computer lock" function is activated on the host PC/Mac
- Secure Entry - Data cannot be accessed without the correct high-strength alphanumeric 8-16 character password. A password hint option is available. The password hint cannot match the password
- Upload the file to OneDrive or a secure SharePoint location.
- Create a sharing link with permissions for the intended recipient.
- Paste the link into your email and send it.
- If the recipient cannot open it, review the link’s permissions and access settings.
A link will not help if it points to a location only you can access. Microsoft’s Outlook attachment guidance explains how to attach files or share them from a cloud location.
Alternative: attach a ZIP archive
Compression changes how a file is packaged; it does not remove malware or prove that the contents are trustworthy. Microsoft documents using a compression utility such as WinZip to create an archive with a different extension. On Windows, you can also use the built-in option described in Microsoft’s troubleshooting steps:
Rank #2
- Certified to FIPS 197 - High-level information security standard approved by the U.S. Government
- Brute-Force Password Attack Protection - Data is automatically erased after 6 failed access attempts. The data and encryption key are securely destroyed and the crypto drive is reset
- Auto-lock - The crypto drive will automatically encrypt all data and lock when removed from a PC/Mac or when the screen saver or "computer lock" function is activated on the host PC/Mac
- Secure Entry - Data cannot be accessed without the correct high-strength alphanumeric 8-16 character password. A password hint option is available. The password hint cannot match the password
- SuperSpeed USB 3.0 - Transfer all your confidential files and folders faster than ever before. Works on both PC & Mac
- In File Explorer, right-click the file.
- Choose Send to, then Compressed (zipped) folder.
- Attach the resulting ZIP file to your Outlook message, if Outlook accepts it.
Microsoft’s Windows attachment troubleshooting guide provides the ZIP steps. A compression utility is optional; Windows includes a way to create a ZIP archive.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWindows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallAlternative: rename the file extension—with caution
Microsoft also documents renaming a blocked file to an extension Outlook does not block, sending it, and asking the recipient to save it and restore the original extension. This changes the visible filename, not the underlying file type or its safety. Because the recipient must know and trust what the file is, use a OneDrive or SharePoint link when possible.
Rank #3
- Certified to FIPS 197 - U.S. Government Approved High Level Information Security Standard.
- Protection against brute force password attacks - Data is automatically erased after 6 unsuccessful access attempts. The data of the USB flash drive type c encryption with dual connectors is destroyed and the cryptographic drive is reset.
- Durable dual-layer waterproof design* — Protects the crypto reader from bumps, drops, run-in and immersion in water. The electronics are protected by a hardened internal case. Rubberized silicone outer case provides a final layer of protection.
- Auto-Lock —The cryptographic key automatically encrypts all data and locks when removed from a PC/Mac or when screen protection or "computer lock" is enabled.
- Secure Entry —Data on these flash drives cannot be accessed without the correct alphanumeric password of 8 to 16 characters. A password indication option is available for this flash drive. The hint cannot match the password.
- Rename the file to an extension Outlook permits.
- Send it only to someone expecting the file, and tell them its original extension.
- Have the recipient save the attachment and restore its original extension before opening it.
Microsoft describes this workaround in its blocked attachments guidance. Do not use it to disguise an unexpected file or bypass your organization’s security rules.
Which option should you use?
| Option | Security and access | When it fits |
|---|---|---|
| OneDrive or SharePoint link | Recipient access depends on correctly set link permissions; use a trusted location. | Best default for sharing a blocked file. |
| ZIP archive | Changes packaging only; it does not make the contents safe. The recipient still needs to receive the archive. | Useful if Outlook accepts the ZIP and the recipient can handle the archive. |
| Rename the extension | Changes the filename, not the file itself; less transparent to the recipient. | Only for an expected, trusted file when the recipient understands how to restore its extension. |
| Ask an Exchange administrator | Any change depends on Exchange configuration and organizational policy. | When permitted workarounds fail or the organization needs to allow a file type. |
If none of the workarounds works
If you use an Exchange account, contact your organization’s administrator. Microsoft says an administrator may be able to unblock certain file types or adjust mailbox attachment settings. Do not treat registry changes as a routine end-user fix; attachment controls may be governed by organization policy.
Rank #4
- FIPS 197 with XTS-AES 256-bit Encryption: Provides business-grade security with hardware-based encryption to protect your sensitive data
- Brute Force and BadUSB Attack Protection: Safeguards against unauthorized access attempts and malicious USB attacks with digitally-signed firmware
- Multi-Password Option with Complex/Passphrase modes: Offers flexible password configuration options to meet various security requirements and user preferences
- New Passphrase Mode: Enhanced security feature allowing users to create longer, more memorable password phrases for easier access without compromising protection
- Dual Read-Only (Write-Protect) Settings: Enables write protection functionality to prevent accidental data modification or deletion when needed
Sharing links and archives can also be restricted by workplace policy. Follow your organization’s rules and ask its IT team which approved transfer method to use.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Check a file before opening it
Only open attachments you expected and trust. If a message or file seems unusual, confirm with the sender through a separate, trusted channel before opening it. Renaming or compressing a file does not establish that it is safe. Microsoft’s guidance on opening and saving Outlook attachments also advises caution with files from unknown or untrusted senders.
Quick Recap
Best Value
- FIPS 140-3 Level 3 (Pending) Certified Military-Grade Security
- OS/Device Independent
- XTS-AES Hardware Encryption
- Enforced Alphanumeric PIN
- Multi-PIN (Admin and User) Option
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
