Email Header: "Return-Path" Contains Unknown Address

If you do not know the email address entered under Return-Path in the email header, this email may have been forwarded to your address through another IONOS mailbox.

If a IONOS mailbox forwards an email, the IONOS mail system stores a coded entry in "Return-Path" according to the so-called Sender Rewriting Scheme(SRS):
 

• The SRS ensures that the original sender of a forwarded email remains recognizable by an entry in the email header. Undeliverable messages can be sent to the original station.
• The entry is created according to the following pattern: SRS0=HHH=TTT=hostname=local-part@domain, where HHH is a hash and TT is a timestamp;
  
  in the following example the email was originally sent from account@example.com:
  
  Return-Path: SRS0=OVdk=H5=example.com=m
  ax.account@srs2.ionos.com