How to Send Secure Email in Outlook: Step-by-Step Guide

Blog, Email Security

Learn how to send secure email in Outlook using built-in encryption options, the subject line method, and best practices to protect sensitive messages in Microsoft 365.

by Yunes Tarada

Last Updated:
5 min read
How to Send Secure Email in Outlook: Step-by-Step Guide
Table Of Contents−

Key Takeaways

  • Outlook uses Microsoft Purview Message Encryption so you can send secure mail without third-party plugins.
  • You can encrypt via the Options tab or by using a subject line trigger like [ENCRYPT] if your admin has set it up.
  • When you encrypt an email, Outlook automatically protects any files attached to that message.
  • You can send secure mail to Gmail or Yahoo users; they just use a one-time passcode to view it.
  • Encryption hides content, but DMARC and SPF prove you are the real sender.

Data breaches and phishing are everywhere right now, so just sending sensitive stuff through a regular email is honestly a huge risk. The good news is Outlook already has built-in tools to protect your messages, so you don’t even have to download extra apps or use random third-party tools.

If you’re sending over a legal contract, bank info, or private health stuff, this guide shows you exactly how to use Outlook encryption to keep your business private. If you want to get into the nerdy side of things, like S/MIME vs. OME, you can check out our guide on how to encrypt email in Outlook.

What Does “Secure Email” Mean in Outlook?

Secure email in Outlook means your message is locked down while it’s flying across the internet and while it’s sitting in an inbox. It really does two main things:

  • Encryption: This turns your email into an unreadable, scrambled format so only the person you actually sent it to can read it.
  • Access Control: This lets you set some ground rules, like stopping the other person from hitting forward or copying what you wrote.

The good news is that it works with any email service, and the person you’re messaging doesn’t have to install any weird software just to open what you sent.

How to Send a Secure Email in Outlook (Microsoft 365 / Classic)

If you use the desktop version of Outlook or the standard Microsoft 365 view, the easiest way to lock down a message is through the Options menu.

Step-by-Step:

1. Open Outlook, click New Email.

2. Go to the Options tab.

3. Click the Encrypt button.

Secure Email

Screenshot taken from the official website

4. Pick any of these options:

  • Encrypt-Only: This scrambles the message but allows the recipient to reply or forward it.
  • Do Not Forward: This encrypts the message and stops the recipient from sharing it further.

Secure Email

Screenshot taken from the official website

5. Write your message, click Send.

Note: You need a specific subscription for this, like Microsoft 365 Business Premium or an Enterprise plan.

What the Recipient Sees

If the person you email also uses Outlook, the message opens normally with a small lock icon. If they use a different service like Gmail, they get a link to a secure portal. They can then sign in with their Google account or use a One-Time Passcode sent to their inbox to read the mail.

Use the Subject Line to Send Secure Email

Many companies set up Mail Flow Rules to make things faster. These rules trigger encryption based on specific words.

How to use it:

1. Start a new email.

2. In the Subject line, type [ENCRYPT] and then add your subject text.

3. Send the email as you normally would.

This is great if you want to stay secure without clicking through menus. Just keep in mind that this only works if your IT admin set it up. You should send a test email to a personal account first to make sure it works for your organization.

How to Send Secure Email Attachments via Outlook

A lot of people ask if their files stay safe, too. When you encrypt an Outlook email, any file you attach is automatically encrypted with the message body.

Extra Protection with Sensitivity Labels

If your office uses Sensitivity Labels, you get even more control over what happens to those files:

1. In the new email window, click Sensitivity.

2. Pick a label like Confidential or Highly Confidential.

3.These labels can automatically encrypt the mail and add rules.

You can also put a password on a PDF or Excel file before you attach it.

How Secure Outlook Email Works with Email Authentication

Encryption protects the content of your mail, but it doesn’t prove who sent it. This is why SPF, DKIM, and DMARC are so important.

A hacker can still “spoof” an email to look like it came from your boss, even if they use encryption. To stop this, services like PowerDMARC can help:

  • Stop Spoofing: Make sure only your authorized servers send mail from your domain.
  • Fix Deliverability: Authenticated mail stays out of the spam folder.
  • Visibility: Use a dashboard to see exactly who sends mail on your behalf.

For a full setup, you can follow our guides on DMARC for Office 365 and Microsoft Office 365 DKIM setup.

Common Issues with Outlook Encryption

Even with built-in tools, you might run into a few digital speed bumps. Here is how to fix them:

  • Recipient can’t open it: They usually need to use the one-time passcode fallback if they aren’t on a Microsoft account.
  • The button is greyed out: This happens if you have a personal “Family” plan or your admin hasn’t assigned the right license to you.
  • Subject line code fails: The [ENCRYPT] method is a manual rule. If it doesn’t work, your IT team hasn’t enabled that specific trigger.
  • Delivery fails: If your secure emails don’t arrive, check if your SPF, DKIM, or DMARC settings are blocking the messages.

Summing Up

Once you know where the buttons are, it’s quite easy to send a secure email. Whether you choose to click that encrypt option or just drop a quick encrypt text in the subject line, you’re doing the most to keep your private info safe. It only takes a second, and it’s way better than dealing with a massive data leak later.

Encryption locks the “envelope,” but it doesn’t always prove you’re the one who actually sent it. If you want to protect your identity and make sure your emails don’t just rot in a spam folder, you’ve gotta check your authentication settings.

Check out our DMARC analyzer to see how PowerDMARC helps stop spoofing and boost your email deliverability.

Frequently Asked Questions

Is Outlook email secure by default?

Outlook uses TLS to protect email while it moves between servers. But it doesn’t protect the message once it sits in an inbox. You have to use the Encrypt button or other email encryption services.

Is Outlook email encrypted in transit?

Outlook uses TLS to keep your mail safe while it’s moving. But TLS only protects the “trip” it takes; it doesn’t stop someone from just hitting forward once the email actually lands in their inbox.

How do I know if my Outlook email is secure?

When you type up a message, look for a padlock icon or a banner that says Encrypted. You can also go to Options, then Encrypt, to double-check.

Is Outlook encrypted email HIPAA compliant?

It can be! You just need a signed Business Associate Agreement with Microsoft, and you have to use encryption for anything with private health data. It’s also a good idea to make sure your domain uses MTA-STS.

Can I send a secure email to someone who’s not in my organization?

Yes, if they sign in with their own account or use the temporary code.

How do I send a secure email in Outlook on Mac?

It’s the same as Windows. Start a new message, hit the Options tab, and click Encrypt. Just make sure your Office app is updated.

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