Last September, we announced new capabilities in Office 365 Message Encryption that enable users to seamlessly collaborate on protected emails with anyone. This release included Do Not Forward an out...
Updated May 11, 2021
Version 11.0
Blog Post
Thats used to happened to us but now it rarely does as recipients start learning the process.
1. If they use Microsoft as an email provider and the address sent to is Microsoft, they can see the encrypted email if they check their email online.
2. If they are using Outlook, it helps if their Outlook is signed into an Outlook account (if they have one) under options -> account.
3. Sometimes they have to double-click the actual email in Outlook and it will download rights real quick.
4. Sometime you have to enable "DecryptAttachmentForEncryptOnly" via Exchange PowerShell. I forgot how.
5. If the email was sent to a distribution list, they will have issues.
6. If they are forwarding an email to someone, the will not be able to sign into the original recepient email to see the email.
It is a matter of just responding to the recipients and having them try different methods that might work and eventually the "should" get it.