This update comes from a user–it’s a pretty simple one.
I posted the script Remove-ProxyAddresses back in 2017 after writing a blog post on the same topic. In my script, I had covered Mailboxes, MailUsers, and Contacts. I did not, however, include RemoteMailboxes, as my original thinking was “if you moved it there, you already got rid of the bad proxies.”
Which, didn’t turn out to be necessarily true (especially if you used my other way of removing proxy addresses via AAD Connect). I also overlooked the fact that you may want need to divest organizations or drop domains for other reasons.
To rectify that, I’ve updated it so it also will allow you to remove proxy addresses for Remote Mailboxes.
Cheers! You can fetch the updated script at https://gallery.technet.microsoft.com/Remove-Exchange-Proxy-eb5be217 and remove addresses to your heart’s content!