By doing a little advance planning on the extensions in your organization, you can make your users more reachable and fully exploit the functionality of the OnSIP Hosted PBX.
Extensions have a max of 6 digits, can start with a 0, but must be at least two-digits; cannot be one digit.
Extensions should be at least four digits and start with a 7
You will have the best success with extensions that are four digits long and start with a seven. Many customers have extensions beginning with a '1' and would like to keep their extensions the same. The first concern with extensions beginning with a '1' is that they may conflict with your "Attendant" Menu. You may, for example, have the option on your Attendant Menu to: “Choose 1 for sales, 2 for customer service, etc.” Then, if the caller chooses '1,' we have to wait four seconds to see if they actually wanted '1' for sales, or if they hit '1' as part of an extension, '101.'
The second concern is with Polycom phones and other phones that have a digit map or internal dial-plan. As soon as the caller dials the '1,' the phone expects you to dial 10 more digits with the next digit being a number between 1 and 9. So, as soon as you dial '10' on your way to dialing '101,' the phone will give you a fast-busy.
Extensions that are four digits long give you the flexibility to designate the third digit (the digit in the 'hundred's place) to something specific, e.g. a voicemail box or cell phone.
Extensions for voicemail boxes, cell phones, groups, and ACD queues
To send calls directly to a user's voicemail box, that voicemail box must have a direct dial extension. To add an extension to a voicemail box, From the Administrators tab choose the "Inbound Call Settings". Then, choose "Voicemail" from the search option locate the mailbox. Give each voicemail box its own extension.
You can do the same for cell phones. To create an external number, go to “Outbound Call Settings” then choose "External Phone Number." Select Add external phone number and enter the phone number, be it a cell phone, home phone, or other frequently dialed external number. “Save and exit”. Once it shows up in the list below, click the drop down and assign the extension.
Similarly, groups and ACD queues can be labeled by their own extensions. ACD Queues and Groups are found under” Inbound Call Settings” . By adding these extensions, you can forward calls to a general queue or group, which would allow any member to answer.
For example, if the extension for the user is 7001, you can create an extension for their voicemail box that is 7701. Do the same for all extensions. Then, if you know someone's extension, just by changing the third digit to a '7' you then know the direct transfer extension for their voicemail box.
You can also do this for cell phones. They could be the '9' extension. Then, when finished, you could have user Sue Smith be extension 7001 for her phone, 7701 for direct transfer to her voicemail, and 7901 to send calls to her cell phone.
The following extension configuration is not recommended: *711 *711x Extensions starting with these digits will go to the TTY Relay Center; *411 *411x Extensions starting with these digits will go to Information; *611 *611x Extensions starting with these digits will report a problem with telephone service (landline service); *911 *911x Extensions starting with these digits will got to Emergency Call Centers if enabled in customer's account.