Each family member needs a mailbox:

The voicemail.conf looks like this:

[general]
format = wav
attach = yes

[default]
; Syntax for new entries looks like this:
; MailboxNumber => password,name,e-mail,pager,options
; (usually, the MailboxNumber is the same as the Extension)
200 => 1234,Dave Robinson
201 => 1234,Colleen Robinson
202 => 1234,Matthew Robinson,matt@robinsonfamily.name
203 => 1234,Lisa Robinson,lisa@robinsonfamily.name,,delete=yes

In extensions.conf, we send an unanswered call to voicemail like so:

[robinson-family]
; If nobody picks up within 30 seconds, the call is sent to voicemail
; If the extension is busy, the call is sent to voicemail
exten => _20[0-3],1,Set(TARGETNO=${EXTEN})
exten => _20[0-3],n,Dial(SIP/${EXTEN},30)
exten => _20[0-3],n,Goto(s-${DIALSTATUS},1)  ; routes the call to the st
atus priority (NOANSWER,BUSY,CHANUNAVAIL,CONGESTION,ANSWER)
exten => s-NOANSWER,1,VoiceMail(${TARGETNO},u) ; Person at extension "is
 unavailable" message
exten => s-BUSY,1,VoiceMail(${TARGETNO},b)     ; Person at extension "is
 busy" message
exten => s-ANSWER,1,Hangup()                 ; To be safe, clean up the 
call after an answer by hanging up
exten => _s-.,1,Goto(s-NOANSWER,1)           ; Handle any unhandled stat
us the same way we handle NOANSWER

; Check your voicemail from your own extension by dialling "250"
exten => 250,1,VoiceMailMain(${CALLERID(num)})

A more elegant implementation can use a macro:

[robinson-family]
exten => _20[0-3],1,Macro(normal|SIP/${EXTEN}|${EXTEN})

exten => 250,1,VoiceMailMain(${CALLERID(num)})

[macro-normal];
;  ${ARG1} - extension(s) being called (e.g. SIP/123&SIP/124)
;  ${ARG2} - Mailbox (usually the same as ${MACRO_EXTEN})
exten => s,1,Dial(${ARG1},30)               ; ring extension for a maxim
um of 30 seconds
exten => s,n,Goto(s-${DIALSTATUS},1)        ; go to status priority (NOA
NSWER,BUSY,CHANUNAVAIL,CONGESTION,ANSWER)
exten => s-NOANSWER,1,VoiceMail(${ARG2},u)  ; Person at extension "is un
available" message
exten => s-BUSY,1,VoiceMail(${ARG2},b)      ; Person at extension "is bu
sy" message
exten => s-ANSWER,1,Hangup()                ; To be safe, clean up the c
all after an answer by hanging up
exten => _s-.,1,Goto(s-NOANSWER,1)          ; Handle any unhandled statu
s the same way we handle NOANSWER

The default settings for each voice mailbox are:

Beyond these default settings, individual departments have additional needs and wants for their mailboxes:

The voicemail.conf for Widgets, Inc. looks like this:

[general]
; Messages are stored in higher-quality WAV format.
format = wav

; E-mail notifications sent by the system have voicemail@widgets-inc.biz
; as the From: address
serveremail = voicemail@widgets-inc.biz

; We set a maximum of 200 messages per mailbox.
maxmsg = 200

; The maximum message length is 5 minutes. The message length is set in 
seconds (5 x 60 = 300)
maxmessage = 300

; We set the text for the e-mail notifications.
; The entire text must fit on one line!
emailbody = Hello, ${VM_NAME},\n\nyou have a new voicemail message from 
${VM_CALLERID} in your mailbox ${VM_MAILBOX}. To listen to your new mess
ages, dial 800.\n\n-- Asterisk Voicemail System\n

; Text for the pager notifications.
; The entire text must fit on one line!
pagerbody = New voicemail from ${VM_CALLERID} at ${VM_DATE}.

; Attach messages to e-mail notifications?
attach = yes

[default]
; Syntax for new entries looks like this:
; MailboxNumber => password,name,e-mail,pager,options
150 => 1234,Building Manager,,pager.buildingmgr@widgets-inc.biz,review=y
es|callback=internal-extensions
802 => 1234,Sales (Domestic)
803 => 1234,Sales (International)
201 => 1234,Chelsea Important,bob.important@widgets-inc.biz,,review=yes|
callback=internal-extensions
202 => 1234,Rick Important,rick.important@widgets-inc.biz,,review=yes|ca
llback=internal-extensions
804 => 1234,Reception,reception@widgets-inc.biz,,review=yes

Calls are sent to voicemail in extensions.conf like so:

[building-mgr]
include => internal-extensions
include => voicemail-buildingmgr

[it]
include => internal-extensions
include => voicemail-easyaccess
include => voicemail-generalaccess

[managers]
include => internal-extensions
include => voicemail-easyaccess

[reception]
include => internal-extensions
include => voicemail-easyaccess

[sales-domestic]
include => internal-extensions
include => voicemail-sales-domestic

[sales-international]
include => internal-extensions
include => voicemail-sales-international

[shipping]
include => internal-extensions
include => voicemail-easyaccess

[production]
include => internal-extensions
include => voicemail-easyaccess

[others]

[macro-simple];
;  ${ARG1} - extension(s) being called (e.g. SIP/123&SIP/124)
;  ${ARG2} - Mailbox (usually the same as ${MACRO_EXTEN})
exten => s,1,Dial(${ARG1},30)               ; ring extension for a maxim
um of 30 seconds
exten => s,n,Goto(s-${DIALSTATUS},1)        ; go to status priority (NOA
NSWER,BUSY,CHANUNAVAIL,CONGESTION,ANSWER)
exten => s-NOANSWER,1,VoiceMail(${ARG2},u)  ; Person at extension "is un
available" message
exten => s-BUSY,1,VoiceMail(${ARG2},b)      ; Person at extension "is bu
sy" message
exten => s-ANSWER,1,Hangup()                ; To be safe, clean up the c
all after an answer by hanging up
exten => _s-.,1,Goto(s-NOANSWER,1)          ; Handle any unhandled statu
s the same way we handle NOANSWER

[internal-extensions]
; If the building manager on duty does not answer the phone,
; the call is routed to mailbox 150:
exten => _15X,1,Macro(simple|SIP/${EXTEN}|150)

; IT has normal mailboxes:
exten => _16X,1,Macro(simple|SIP/${EXTEN}|${EXTEN})

; Each manager has his or her own mailbox:
exten => _20[1-2],1,Macro(simple|SIP/${EXTEN}|${EXTEN})

; The reception staff have a common mailbox:
exten => _2[3-6]X,1,Macro(simple|SIP/${EXTEN}|804)

; The domestic sales group has a common mailbox:
exten => _3[0-4]X,1,Macro(simple|SIP/${EXTEN}|802)

; The international sales group has a common mailbox:
exten => _3[5-9]X,1,Macro(simple|SIP/${EXTEN}|803)

; No voice mail on the other extensions.
exten => _[4-5]XX,1,Dial(SIP/${EXTEN},30)

[voicemail-easyaccess]
exten => 800,1,VoiceMailMain(${CALLERID(num)})

[voicemail-generalaccess]
exten => 801,1,VoiceMailMain()

[voicemail-buildingmgr]
exten => 800,1,VoiceMailMain(150)

[voicemail-sales-domestic]
exten => 800,1,VoiceMailMain(802,s)

[voicemail-sales-international]
exten => 800,1,VoiceMailMain(803,s)

The extensions.conf for Widgets, Inc. is already starting to look a bit more complicated. This is because we are using different mailbox features for different users and departments. There are normal individual mailboxes for some staff and group mailboxes for sales and reception; on top of that, sales staff must be able to access messages without having to enter a password. This must be as easy and transparent as possible for individual staff members, so we set the standard voice mailbox access number to 800 for everyone.