Link leading to attachment gives 404 Not Found error message
You or one of your subscribers reports that an attachment sent to your list is missing.
You are using the Clickable Attachments feature - See http://help.mail-list.com/m/59114/l/558203
The web page says
The link in the email was something like -
That link has expired, based on your settings for the Clickable Attachments
Unless you have changed the default setting, any attachments will be deleted after 1 month.
You can change that setting to prevent this from happening in the future.