Email Header: "Return-Path" Contains Unknown Address

If you do not know the e-mail address entered in the e-mail header under Return-Path, this e-mail may have been forwarded to another IONOSmailbox at your address.

If a IONOSmailbox forwards an e-mail, the IONOSmail system stores an encoded entry in "Return-Path" according to the so-called Sender Rewriting Scheme (SRS):

  • By making an entry in the e-mail header, the SRS ensures that the original sender of a forwarded e-mail remains recognizable. Undeliverable messages can be sent to the original station.
  • The entry is created according to the following pattern: SRS0=HHH=TT=hostname=local-part@domain, where HHH stands for a hash and TT for a timestamp. In the

    following example, the e-mail was originally sent from the address