Configure Mailman as an announce-only Newsletter list
Mailman is created mainly as an application for discussion groups, when everyone can post a message that will be mailed to everyone, however you can configure it as a powerful one-way post list, for occasional announcements or your weekly newsletter…
1) Open the configuration web page of your list (usually at your-domain/mailman/admin/your-list-name_your-domain/general). As you see the configuration page opens in the General Options section.
2) Define the list admin and moderator addresses (the same address can be used for both). In the same (General Options) page, you can “Hide the sender of a message, replacing it with the list address“. Perhaps it would be more professional and safe to use the address of the list itself as the sender, but sometimes certain servers may consider such mail as spam.
3) In the same page (General Options), Choose “Yes” in the option, “should any existing Reply-To header found in the original message be stripped?“, and in the next option “Where are replies to list messages directed?“, choose an “explicit address” and define this address. It can be a “trash” address, a forwarder, whatever, according to what you are going to do with these messages – just ignore them, or check if someone tries to contact you with a question.