Debian 12 exim 4.96 SRS Unrouteable address

When an e-mail arrived to a SRS0=… recipient, the exim bounce this e-mail with “Unrouteable address”

How to reproduce:

  • Fresh debian 12 + hestiacp install
  • Add a domain (and configure dns properly) (call it example . com)
  • Add an e-mail address to the domain (let it test @ example . com)
  • Add a forwarder to this e-mail. (let it my-own-test @ gmail . com)
  • Set an automatic answer on my-own-test @ gmail . com
  • Send an e-mail from any other address to test @ example . com (let it otheruser @ otherexample . com)

What will happen:

  • The test @ example . com forward the mail to my-own-test @ gmail . com. In this mail the envelope sender wil be similar to: [email protected]
  • the gmail will send back the automatic reply (or any error message) to this SRS0=… address
  • the exim at will bounce this mail back to my-own-test @ gmail . com with “Unrouteable address” error.

How let the exim to recognise this SRS0=… address, and forward the mail to otheruser @ otherexample . com?