Exim4

Conditional rewrite

https://exim-users.exim.narkive.com/cjDiulLN/rewrite-sender-based-on-recipient

Example: 1. set acl_c1 to some address if session is from some stupid host that cannot specify valid sender address 2. add this to rewrite section:

* "${if !eq{$acl_c1}{} {$acl_c1} fail}" Ff