How to Send a Secure Email in Outlook: Encrypt, Protect & Send Encrypted Messages with Microsoft 365

If you’re searching for how to send a secure email in Outlook, you’re in the right place. At mail experts, we help businesses protect sensitive information, prevent data leaks, and stay compliant using advanced Microsoft 365 and Office 365 message encryption solutions.

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In today’s threat landscape, sending a standard email in Outlook without protection is a risk. Cybercriminals target unencrypted messages, intercept attachments, and exploit weak configurations across email servers. That’s why understanding how to encrypt emails, send encrypted communications, and use built-in encryption features in Microsoft Outlook is essential.

This comprehensive commercial guide will show you:

How to send encrypted messages in Outlook
How 365 message encryption works
How to configure Microsoft 365 message encryption properly
How to decrypt and read the encrypted message as a recipient
When to use encryption and digital signatures
How to protect outgoing messages automatically
And how mail experts can secure your entire email ecosystem

If your business needs professional-grade protection, explore our dedicated service:
👉 Business Email Security Services:
https://mailexperts.io/services/business-email-security/

If you also use Gmail, read our related guide here:
👉 https://mailexperts.io/how-to-send-secure-email-gmail/

Now let’s break down everything you need to know about sending encrypted email in Outlook.

Encryption in Outlook: Why It Matters for Microsoft 365 Users

Understanding Email Encryption in Microsoft Outlook

Encryption converts readable message content into coded data that only the intended recipient can access. When you encrypt emails in Microsoft Outlook, the message and its contents and attachments are protected both in transit and at rest.

Without encryption:

Email message content travels through multiple email servers
Attachments can be intercepted
Sensitive information can be exposed
Unencrypted communication may violate compliance rules

With proper Microsoft 365 message encryption, your message is:

Encrypted using secure standards
Protected with a one-time passcode or Microsoft account verification
Restricted to the intended recipient
Prevented from forwarding if you choose “Encrypt or Do Not Forward”

This is how encryption works inside 365 Outlook environments.

How to Send Encrypted Email in Outlook (Step-by-Step)

Method 1: Send an Encrypted Email in Outlook for Windows (Outlook for Windows Versions 2019 & New Outlook)

If you’re using Microsoft Outlook desktop:

Open Outlook.
Click New Message.
Enter recipient, subject line, and email message content.
Go to the Options tab.
Click Encrypt.
Select your preferred encryption options:
- Encrypt-Only
- Do Not Forward
Send a message normally.

When you select encrypt, Outlook applies 365 message encryption automatically if your organization has a valid 365 subscription.

This ensures the message is encrypted using Microsoft’s security protocols before delivery.

Method 2: Send Encrypted Email in Outlook on the Web (Outlook.com / Microsoft 365)

If you’re using Outlook on the web:

Log in to your 365 account.
Click New message.
Click the three dots (More options).
Select Encrypt.
Choose encryption options.
Send encrypted.

When sending encrypted email this way, recipients may:

Sign in with a Microsoft account
Obtain a one-time passcode
Access a secure web portal
Read the encrypted message securely

This works across email providers.

Method 3: Outlook for Mac

Using Outlook for Mac:

Create a new message.
Click Options.
Choose Encrypt.
Select encryption and digital signatures if needed.
Send an encrypted email.

Outlook for Mac supports both Office 365 message encryption and digital certificates.

Method 4: Outlook for iOS and Android

In Outlook for iOS and Android:

Start a new message.
Tap the three dots.
Select encryption.
Send encrypted.

Mobile encryption protects outgoing messages even when sending from smartphones.

Office 365 Message Encryption Explained

What Is Office 365 Message Encryption?

Office 365 message encryption (OME) is built into Microsoft 365. It allows organizations to:

Automatically encrypt outgoing messages
Protect sensitive information
Prevent forwarding
Restrict message content access
Control attachments

OME works with:

Outlook for Windows
Outlook for Mac
Outlook on the web
Outlook.com
Outlook for iOS and Android

It integrates with Microsoft Purview compliance policies.

Microsoft 365 Message Encryption and Purview Integration

How Microsoft Purview Enhances Email Security

Microsoft Purview allows businesses to create compliance rules that:

Automatically encrypt messages containing sensitive data
Apply encryption based on keywords
Protect financial or health records
Enforce encryption features organization-wide

This is critical for businesses handling:

Customer data
Contracts
Payment details
Confidential attachments

At mail experts, we configure Purview policies for businesses that need enterprise-level email security.

Encryption Options in Outlook

When sending encrypted email in Outlook, you may see several encryption options:

1. Encrypt-Only

Protects message content
Recipient can reply to encrypted messages
Cannot remove encryption

2. Encrypt or Do Not Forward

Prevents forwarding
Blocks copying
Restricts printing
Limits sharing

3. Digitally Sign

You can also digitally sign a message using digital certificates and a public key infrastructure. This confirms:

Sender identity
Message integrity
Authenticity

How Recipients Read the Encrypted Message

When you send an encrypted message:

The recipient receives a message with instructions.

They can:

Sign in with Microsoft account
Obtain a one-time passcode
Use a secure web portal
View the message
Open the attachment securely

If they use Outlook:

They may directly read the encrypted message inside their email client.

If they use other email providers:

They authenticate and decrypt via passcode.

This ensures end-to-end protection.

How to Decrypt an Encrypted Email in Outlook

If you receive encrypted email in Outlook:

Open the email message.
Authenticate using your Microsoft account.
Enter passcode if required.
Read the encrypted message.
Reply to encrypted messages securely.

If using non-Outlook email accounts, you may decrypt through the web portal.

TLS vs End-to-End Encryption in Microsoft 365

TLS Encryption

TLS protects messages during transit between email servers.

However:

Once delivered, message content may not remain encrypted.

End-to-End Encryption

End-to-end encryption ensures:

Only sender and intended recipient can read message content.
Even Microsoft cannot access it.
Attachments remain protected.

Microsoft 365 message encryption provides layered protection beyond TLS.

Encryption and Digital Signatures: When to Use Both

Use encryption when:

Sending sensitive information
Sharing confidential attachments
Handling legal documents

Use digital signature when:

Verifying identity
Proving authenticity
Preventing tampering

Combining encryption and digital signatures provides full security.

How to Encrypt a Single Message in Outlook

If you don’t want automatic rules:

Create new message.
Choose to encrypt.
Encrypt the message manually.
Send encrypted.

This method works even if you only need to send secure email occasionally.

Automatically Encrypt Outgoing Messages

Using Microsoft 365 policies, you can:

Automatically encrypt based on subject line
Trigger encryption based on message content
Protect attachments automatically
Apply rules organization-wide

This eliminates human error.

At mail experts, we implement automation so you never accidentally send unencrypted communication again.

Why Businesses Must Send Secure Email in Outlook

Risks of Unencrypted Emails

Data breaches
Financial fraud
Reputation damage
Compliance violations
Legal exposure

Sending encrypted email is no longer optional.

How Mail Experts Secures Your Microsoft 365 Outlook Environment

While learning how to send a secure email in Outlook is important, configuration mistakes can still leave vulnerabilities.

Our services include:

Full Microsoft 365 audit
Purview compliance setup
Office message encryption configuration
Digital certificates management
Email security hardening
Secure attachment protection
Advanced encryption features deployment

👉 Explore our business email security service here:
https://mailexperts.io/services/business-email-security/

Common Problems When Sending Encrypted Email

Issue 1: Encrypt Option Missing

Possible causes:

No 365 subscription
License not assigned
Incorrect policy configuration

Issue 2: Recipient Cannot Read the Message

They must authenticate
They may need to obtain a one-time passcode
Check spam folder
Ensure correct email address

Issue 3: Attachments Not Opening

Encrypted attachments must be opened after authentication.

If problems persist, contact Microsoft support or a certified provider like mail experts.

Outlook Encryption Across Different Versions

Version	Encryption Supported
Outlook for Windows versions 2019	Yes
New Outlook	Yes
Outlook for Mac	Yes
Outlook on the web	Yes
Outlook.com	Yes
Outlook for iOS and Android	Yes

All modern versions of Microsoft Office support encryption.

Best Practices for Sending Encrypted Email in Outlook

Always encrypt financial documents.
Use strong passcode methods.
Avoid sending sensitive information unencrypted.
Digitally sign executive communications.
Train staff on encryption options.
Test decryption workflows.
Monitor email servers.
Apply automatic encryption rules.

Frequently Asked Questions About Sending Encrypted Email in Outlook

How do I send an encrypted email in Outlook?

Open a new message, select Encrypt, choose encryption options, and send.

Can I encrypt attachments?

Yes. When you encrypt the message, contents and attachments are encrypted.

Does recipient need Outlook?

No. They can authenticate via web portal.

Is Microsoft 365 message encryption secure?

Yes. It uses modern encryption standards and compliance frameworks.

Why Choose Mail Experts for Microsoft 365 Encryption Setup?

Because sending encrypted email properly requires:

Correct license configuration
Policy creation in Purview
Digital certificates setup
Public key management
Compliance alignment
Email security architecture expertise

At mail experts, we go beyond basic setup.

We provide:

Enterprise-grade configuration
Threat monitoring
Compliance readiness
Advanced encryption strategies
Full Microsoft 365 security optimization

Final Thoughts: Mastering How to Send a Secure Email in Outlook

Understanding how to send a secure email in Outlook is essential for modern businesses.

Whether you’re using:

Outlook for Windows
Outlook for Mac
Outlook on the web
Outlook for iOS and Android
Office 365
Microsoft 365

You must encrypt emails consistently.

Sending encrypted email protects:

Sensitive information
Attachments
Message content
Business reputation
Customer trust

If you need help implementing secure, automated, compliant encryption inside Microsoft Outlook, partner with professionals who specialize in email security.

👉 Secure your organization today:
https://mailexperts.io/services/business-email-security/

👉 Also read our Gmail guide here:
https://mailexperts.io/how-to-send-secure-email-gmail/

Mail Experts — Protecting your email with Microsoft 365 encryption, Office 365 message encryption, and enterprise-grade security solutions.