The message can be retrieved by the recipient - a person or a mailbox - at any time. Voice mail systems must support individual user scenarios such as time- and date-dependent call forwarding. In addition, they should be able to be retrieved via e-mail and the message should also be able to be sent as an attachment.
Voice mail systems are similar to answering machines. Their development ranges from the simple voice mailbox to Interactive Voice Response( IVR), which can be used to control computers and query databases.