From your description, it appears there might be a challenge with how encoded emails are handled on the Microsoft Purview side, particularly when it comes to decoding those emails for use in collections.
Indeed, URL encoding is a standard practice for handling special characters in URLs or API calls. However, if Purview isn't correctly decoding the email addresses before using them, it could lead to issues as you've described. If emails are not being decoded automatically by Purview, and this is causing collection failures, this may be a more complex issue that requires direct support from Microsoft. While I would recommend reaching out to Microsoft Support for further assistance, here's a potential workaround:
- Preprocess Email Addresses: Before adding them to your case, you could preprocess your email addresses to replace special characters with equivalent acceptable characters. For example, replacing '#' with 'HASH', '_' with 'UNDERSCORE', etc. This way, you're avoiding the encoding-decoding problem altogether.
Remember, this is a workaround and might not be feasible depending on your specific requirements or the volume of email addresses you're dealing with. Therefore, contacting Microsoft Support might still be the best course of action.