Email License not transferring

You do not need another license to use Microsoft Purview Message Encryption in both classic and new Outlook: Office 365 Enterprise E3 includes that entitlement. In new Outlook, compose a message and select Options → Encrypt → Encrypt or Do Not Forward.^1^

First determine which encryption method you use

Classic Outlook may be using either Purview Message Encryption or S/MIME, and the distinction affects both migration and replies:

• Purview encryption: In new Outlook, use Options → Encrypt, choose Encrypt or Do Not Forward, compose the message, and select Send.^2^
• S/MIME: This is certificate-based. In new Outlook, open Settings → Mail → S/MIME and configure the certificate options. For one message, use Options → More Options, then select Encrypt this message (S/MIME). New Outlook requires the external recipient’s certificate on the local computer when sending S/MIME-encrypted mail externally.^2^

Do not apply Purview/IRM protection to a message already signed or encrypted with S/MIME; remove the S/MIME protection first.^1^

If the Encrypt button is missing in new Outlook

Ask your Microsoft 365 administrator to verify:

1. The affected mailbox itself has the Office 365 E3 license assigned—not merely the account used to activate desktop Office. Each user benefiting from Purview Message Encryption requires an eligible license.^3^
2. Microsoft Purview Message Encryption/IRM is enabled and configured for the organization.
3. The same licensed work or school mailbox is selected in the From field when composing.
4. Encryption works in Outlook on the web using New message → Options → Encrypt. Purview encryption supports sending from Outlook and Outlook on the web.^4^

Interpret that test as follows:

• Works on the web but not in new Outlook: the entitlement and service configuration are likely available; have IT investigate the new Outlook client/account state.
• Missing on the web too: this points to mailbox licensing, IRM configuration, or service-side policy. The administrator should review the tenant configuration and open a Microsoft 365 support request if necessary.
• You use Double Key Encryption: it is not supported in new Outlook, so continue using a supported client or have the administrator choose another protection method.^1^

About not receiving a reply

Encryption does not itself guarantee a read receipt or reply.

• With Purview Message Encryption, recipients can reply from supported Outlook clients; users on other mail services can use the encrypted-message portal. Purview also encrypts replies to messages protected by an encryption mail-flow rule.^4^
• If by “reply” you mean an S/MIME receipt, it must be requested explicitly and the message must also be digitally signed. In new Outlook, select Options → More Options, enable the desired read/delivery receipt, and select Digitally sign this message (S/MIME).^2^
• If the recipient says Reply is unavailable or their response never arrives, record the encryption type, recipient mail service, and any non-delivery report. That is a mail-flow or recipient-access investigation, not evidence that another sender license is required.

References

1. Security and compliance in new Outlook for Windows
2. [New Outlook](https://support.microsoft.com/outlook/mail/send-s-mime-or-microsoft-purview-encrypted-emails-in-outlook)
3. Message encryption FAQ
4. Message encryption