Implement New-AddressRewriteEntry / Email Address Rewriting
Why has this been removed from Exchange Online? It has been in the on-premise solution for years ...
Address rewriting modifies email addresses of senders and recipients in messages that enter or leave your organization through an Edge Transport server.
Rikard Strand commented
Would be nice if someone from the Exchange team could comment on this ticket. For my case I'm doing a more from a on-prem system that supports this (domain alias(es) => domain) - and not being able to perform this native in Exchange online (incoming) prevents me from moving a large organization (a customer) to "pure cloud".
Victor Ivanidze commented
As a workaround you can use a third-party cloud service that provides the address rewriting functionality.