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Just please set up DMARC so it allows forwarding a mail... Have had this problem a number of times lately, companies sending mail to us that just vanish in thin

by Moru 6y ago

Just please set up DMARC so it allows forwarding a mail... Have had this problem a number of times lately, companies sending mail to us that just vanish in thin air without any explanation. Turns out an alias adress is forwarding their mail to whoever is supposed to handle their mail at the moment and this is not allowed due to how they set up DMARC. The mail server just drops the mail without warning.

beermonster 6y ago
O2's billing emails, and a well known bank have broken DKIM signatures as they are improperly forwarded. No chance of getting through to their tech support, especially since these types of email are usually from a no-reply@ address and the people manning the phones are not the mail server admins anyway.
- yread 6y ago
  try emailing postmaster@
  - beermonster 6y ago
    No joy there either, sadly.
Volundr 6y ago
If forwarding is failing DMARC, that's on your system, not the senders. There is nothing the sender can do to help the situation. Basically DMARC needs either DKIM OR SPF to pass to consider a message passing. Being no SPF record will ever include (forwarders aren't allowed to originate messages from the domain) that means DKIM has to pass. DKIM works by signing the message body and selected headers with a private key, while the public key is published to DNS. This allows a receiver to fetch the public key from DNS and validate it was really sent by the sender. It should be clear at this point that you'll be able to forward a DKIM signed message as much as you want as long as you don't modify the message when sending. If on the other hand your forwarder modifies the headers (including subject) or the body DKIM will fail. In other words, if your going to use a forwarder, make sure that forwarder will forward the message as is. You can add headers, but don't remove or modify any existing headers and don't modify the message itself.

by Moru 6y ago

beermonster 6y ago

O2's billing emails, and a well known bank have broken DKIM signatures as they are improperly forwarded. No chance of getting through to their tech support, especially since these types of email are usually from a no-reply@ address and the people manning the phones are not the mail server admins anyway.

yread 6y ago
try emailing postmaster@
- beermonster 6y ago
  No joy there either, sadly.

Volundr 6y ago

If forwarding is failing DMARC, that's on your system, not the senders. There is nothing the sender can do to help the situation. Basically DMARC needs either DKIM OR SPF to pass to consider a message passing. Being no SPF record will ever include (forwarders aren't allowed to originate messages from the domain) that means DKIM has to pass. DKIM works by signing the message body and selected headers with a private key, while the public key is published to DNS. This allows a receiver to fetch the public key from DNS and validate it was really sent by the sender. It should be clear at this point that you'll be able to forward a DKIM signed message as much as you want as long as you don't modify the message when sending. If on the other hand your forwarder modifies the headers (including subject) or the body DKIM will fail. In other words, if your going to use a forwarder, make sure that forwarder will forward the message as is. You can add headers, but don't remove or modify any existing headers and don't modify the message itself.