How To Silently Eat Out Of Office Replies
Some of your subscribers may turn on an option in their email reader to reply to all incoming messages with a notification that they are on vacation, and unable to respond.
We do not want those vacation notices to be sent to the mailing list
There are many, many variations of this feature.
Some are implemented in the email reader, like Outlook or Apple Mail.
Others are implemented at the corporate or university system level.
This option is on by default
If you want to turn it off for some reason