Configure the Field Context by adding field rules for each possible sender domains with the following attributes:
Field Rules of these type will implement email routing based on the sender's email address.
However, following the same logic, you can route emails to different projects also based on recipient addresses, email subject and body content etc.
Project routing works if the issue type (and the corresponding workflow) is the same in all projects to which the routing is configured.
If you successfully routed your emails to different projects, you may want to comment the issues from any subsequent emails via the same Mail Handler.
Similaryl, if you want to initialize issue fields or execute workflow transitions for subsequent emails that are related to issues, make sure your Field Context includes the projects or add Field Contexts for each projects you are routing to.