Voice Mail and mailbox should have option be disabled from web interface.

If I want disable mailbox and voicemail for extension I do the the following steps.

1. Log in to web interface.
2. Open corresponding extension settings.
3. Disable voicemail.
4. Clear mailbox filed.
Save
Exit

This is the error

{noformat}
[2012-10-24 20:08:38] ERROR[32754]: app_voicemail.c:2414 inboxcount2: Couldn't find mailbox device in context default
[2012-10-24 20:09:08] ERROR[32754]: app_voicemail.c:2414 inboxcount2: Couldn't find mailbox device in context default
[2012-10-24 20:09:39] ERROR[32754]: app_voicemail.c:2414 inboxcount2: Couldn't find mailbox device in context default{noformat}

It cause by 2 think.

1 We disabled voicemail that mean removed extension from voicemail.conf
2 mailbox= line in sip_additional.conf should be removed or commented out.

Each time when you save config it override values and set mailbox=to default value which produce error, because asterisk can't find this in voicemail context.