Address re-writing not working for Calendar invites

Hi,

We are running a hybrid environment with 3 active directory domains, 3 on-prem Exchange clusters and the majority of our mailboxes in O365.

We have set up a default address rewrite so that emails from everyone across the 3 different legacy domain names appear to come from the new domain name. Lets use an example

mailto:john@company1.com

mailto:john@company2.com

mailto:john@company3.com

Address rewrite is set up so all emails from the above addresses are displayed to external recipients as:

mailto:john@newcompanyname.com

This works perfectly for all outbound emails, however it does not work with meeting/calendar invites.

For example, my own mailbox has the default alias of @company1.com, and when I send an email to a recipient outside of our organisation, it shows as coming from @newcompanyname.com, but when I send a meeting/appointment to an external recipient, it shows as coming from @company1.com.

Has anyone seen this before, if so - do you have any tips on where to start the troubleshooting process?