Abstract: X-RZG-FWD-BY means that an e-mail cannot be delivered (address wrong or out of date) and therefore was forwarded to another similar address.
Each e-mail contains a header containing sender, addressee(s) and subject. Besides these there are more entries which are hided mostly. The description of most entries is well known and described multiply. Some days ago, however, I found an entry for which a looked in the internet without success. Therefore I publish this here. It is the entry with keyword X-RZG-FWD-BY. The complete entry was
Anybody had sent a mail to email@example.com. This address does not exist, as there should be a hyphen between edv und abmayr instead of a point. After some minutes the sender received a mail from the mailserver which told him that the mail could not be delivered to firstname.lastname@example.org. (Yes, this is a quite different address than I had entered.) This mail from the mailserver contained the original mail of the sender as an attachment. And the header of that attached mail contained the above entry. So, the first meaning of the entry seems to be: address of receiver is illegal, may be misspelt or out of date.
Analyzing the problem I found another point: If a mail cannot be delivered, the mailserver tries to send it to another address which is similar to the original (bad) one. In one case the mailserver sent it to another address at edv-abmayr.de (with hyphen) and I received it there. In another case the mailserver sent it to a no longer valid address that contained the name abmayr and belonged to my uncle. So, the second meaning of the keyword (FWD = forward) could be that the undeliverable mail was forwarded to any other similar address which is known by the mailserver for any reason.
BTW: Do you think, this automated forwarding by the mailserver is OK? If you mistype the address of the receiver, anybody else could get your mail !
The mail mentioned above contained a further entry:
This seems to be a classification of the reason why the mail could not be delivered and / or was forwarded.
Author: Bernhard Abmayr, www.edv-abmayr.de, version of November , 24th, 2011