A sender usually would be notified if the destination mail server expressly rejected the message ''before the connection was closed.'' Common reasons for this include a mistaken email address or a policy violation (e.g., spammy message). A sender also is usually notified if the destination mail server does not accept the message within a reasonable period of time for non-permanent reasons (e.g., the server is down). After the destination mail server (or front-end filter) accepts a message, it could be delivered to the intended mailbox, or it could be filtered as viral or spammy, all without any further indication to the sender as to what happened.