There are 2 ways that you can provide access to voicemail remotely. Either by using an option in an Automated Attendant Menu as per the example below which uses “*” to gain voicemail access (see example below).
To configure access the Star2Star web portal 
PHONE SYSTEM CONFIGURATION section see example below / left. Under Advanced Settings click the Automated Attendants link see example below / right. The AUTOMATED ATTENDANTS configuration screen will appear. Click the dropdown to display Menus configured for your system or "Add New Automated Attendant". Select the menu you wish to edit. Pick an option on the menu i.e. “*” and click the drop down selection and pick Applications – Voice Mail Access. Remember to Save Changes to System when you are done making changes.
Or alternatively you can configure a DID / Number to point to the Voice Mail Access application. Voice Mail Access is a pre-defined system application. When accessed, you will be prompted for your extension id and password.
