Proxy Email showing up instead of primary email address in Outlook, how can I fix this?

Question

Hello,

A user's email is showing their proxy address instead of their real email. What is the proper way to fix this issue as the admin.

For more context when making a new user, I will create them in AD, and under Attribute Editor I find the procy address section and add SMTP: ******@domain.com and I add smtp: ******@domain.onmicrosoft.com. So the second, onmicrosoft, email shows up instead of the actual one.

Things I've tried:

1. Verify the Proxy Addresses: Ensure that the primary email address is correctly set with the SMTP: prefix (uppercase) and the secondary email address with the smtp: prefix (lowercase). This distinction is crucial as it determines which address is considered the primary one.

Done.

Check for Conflicts: Make sure there are no conflicting proxy addresses in AD or Azure AD. Conflicts can cause synchronization issues and result in the wrong address being displayed. You can use tools like Azure AD Connect to identify and resolve these conflicts

Done.

Update the Proxy Addresses: If the primary email address is not being recognized correctly, you may need to update the proxyAddresses attribute directly in AD. Ensure that the primary email address is listed first with the SMTP: prefix.

Done.

Synchronize AD with Azure AD: After making the necessary changes in AD, ensure that the changes are synchronized with Azure AD. This can be done using Azure AD Connect. Verify that the changes have been propagated correctly.

Can't Access this.

Check Email Clients: Sometimes, email clients may cache old information. Ensure that the user's email client is updated and that any cached information is cleared.

Done.

Is there something I can do without using Azure AD cconnect?