User does not have to wait during the delivery handling. Automatic resending if the recipient is not available can be done without trouble for the sender. Recipient can download a selection of newly arrived messages. Disadvantages Transmission time can be longer. Reliability can be lower, there are more places where a message can disappear.
Cost can be larger, and there can be problems paying for the relaying servers.
Sender does not get immediate feedback of delivery results. 4 Discuss the handling of error messages, saying that an e-mail message could not be put into the mailbox of the recipient, in the case where the message was sent via a mailing list. The original sender should, however, get a non-delivery notification if the message could not be delivered to the list expander. Non-delivery notifications are then returned to the envelope sender, not to the sender specified in the heading of the message.