In its simplest form it has only the functions of an answering machine, using a standard telephone handset for the user interface, but it can use a centralized, computerized system rather than equipment at the individual telephone. Voicemail systems can be much more sophisticated than answering machines in that they can:

• answer many phones at the same time
• store incoming voice messages in personalized mailboxes associated with the user’s phone number
• enable users to forward received messages to another voice mailbox
• send messages to one or more other user voice mailboxes
• add a voice introduction to a forwarded message
• store voice messages for future delivery
• make calls to a telephone or paging service to notify the user a message has arrived in his/her mailbox
• provide message notification by SMS, a special dial tone, or using Caller ID signalling.
• transfer callers to another phone number for personal assistance
• play different message greetings to different callers.