Why do messages sent via mailman display the from address as something like “From listname-bounces+jim=reader.domain.com@mailman.server.com On behalf of fred@poster.domain.com”?

Most of us expect the From: address to display the person who actually sent the message, not a strange bunch of gobbly-gook.

This is an unfortunate problem that only affects Microsoft Outlook. In other words, only the subscribers of your list who use Microsoft Outlook as their email program will experience this situation. Everyone else will see the person who sent the message in the From field.

The short explanation is:

Every message sent has to “header” fields:

  • From – The name and/or email address of the person who sent the message
  • Sender – The agent (person or software program) that is responsible for sending the email. This field is optional and is only needed if it is different from the from address.

With normal email, the sender field is not necessary. However, with mailman, the sender field is used to process bounce messages. All that gobbly-gook is used by mailman to keep track of which subscribers our bouncing their email so they can be unsubscribed from the list.

Outlook is the only email reader (that we are aware of) that displays the Sender address instead of the From address. There are some ways we could hack our mailman version to get around this Outlook problem, however, we don’t think it is a stable way to provide these services.

A more detailed explanation of the problem is available here:

 http://wiki.list.org/display/DOC/From+field+displayed+by+Microsoft+Outlook

This problem with Outlook affects other services as well, including  gmail.

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