On 10/28/2015 02:22 AM, Marco Stoecker wrote:
I think I do now understand why duplication is happening. But have no idea how to avoid it. So here is how I think it happened.
I send an email to list1 and list2 now on my ISP there is an email forwarding from list1@... and list2@... to the email account mailmansrv@mydomain. So here I have 2 emails in that account which are both to: list1 and list2. Fetchmail now will get these 2 messages with to: to both lists and even postfix gets 2 messages with each adressed to two lists. I think this is the reason why duplication happens. But now I have no glue how to configure on the ISP side or postfix(relayhost) or mailman to avoid such duplicates. Any assistance possible here in this mailing list?
Yes. That is what's happening
To fix this, if it is possible to eliminate fetchmail and have the ISP email forwarding go directly to your machine, you can then configure Postfix on your machine to deliver to Mailman with aliases in the normal way and the problem is solved.
If it is not possible to to eliminate fetchmail because, e.g., it is not possible to mail directly to your machine from the ISP, then perhaps you can eliminate the forwarding from list1@... and list2@... to the email account mailmansrv@mydomain and have fetchmail pick up the mail individually per list and deliver only to that list.
Your basic problem is that mailman is designed to run on the server that receives the list mail directly. Because of whatever restrictions exist that prevent that, you (or someone) have come up with this fetchmail kludge and it doesn't work because of the duplication.
Others have made this work by having separate mailboxes on the host for each list, list-owner, list-subscribe, etc. address and using fetchmail to deliver mailbox by mailbox to the appropriate place on the Mailman machine.