If you send a message, and you suddenly receive a returned mail message. Ignore it. Or just send a private e-mail to the owner of your list, as in:
firstname.lastname@example.orgInclude a copy of the returned-mail message. The list-owner has the tools to deal with it. The problem is usually one subscriber's bad address. They may have mistyped it when they subscribed, or their account may have been discontinued.
Especially, KEEP CALM when your list suddenly receives some commercial ads or junk mail. If you reply to the entire list complaining about it, you just keep the ad in front of everybody. As everybody jumps in and replies, the ad is repeated over-and-over. The best response is to ignore, and they will go away.
There once was a business management list that one day received two ads. Many members reacted with outrage, and the list soon became about controlling ads and junk mail, and the issue of commercialism on the Internet. Angry members now attacked each other. Many others could not stand the arguing, and unsubscribed. For over three weeks there was heavy mail traffic, but not one discussion about business management.
Remember, KEEP CALM....;-)