I have one extension that can receive calls from other extensions, but cannot receive calls from outside. The extension for example is 521. If I dial 521 from another office phone, the extension will ring fine and user can answer. If I dial this number from my cell phone, all I hear is Extension Doesn't exists.

i am not sure, may be i need to configure the mailbox for this extension.

Please guide me how to do it.
Thanks in advance for your help.

Sounds like your outside calls come into an AA and there is no mailbox setup for that ext. We need more info though. What system, What Voice Mail, and are outside calls routed directly to the AA or does it go to a ring group or directly to the extension?

yes i think there is no mailbox setup for that extension.

Aspire m/l system. yes outside calls are routed to the AA,

Can you please guide to how to create a mail box for that extension.

If you have an NEC Voice Mail (my guess would be the AspireMail) Then you will have to login to the programming interface, which is something that you will have to have a tech do unless you know how to do that already, then you will have to create a new subscriber mailbox.

can you please guide me with basic steps i will try to find out the solution. because i am from India and no one is here to help on the programming.

If there is not a dealer or installer in your area your best bet would be to contact one of the moderators on this forum.