What is mt 999?

Question

What is mt 999?

Answer 1

This error appears to be a "catch-all" error code that Yahoo serves up when it doesn't have a more specific error code.

It essentially means "Oops! Something went wrong but we don't know what, so we'll just say that Error 999 occurred."

The most common reason for receiving Yahoo Error 999 is due to some sort of bandwidth limiting system that Yahoo has put in place on their servers.

Once you have exceeded your allotted bandwidth for a specific period of time Yahoo gives you this Error 999 message and doesn't allow you to access the service.

People have primarily reported receiving this error when they try to access Yahoo Mail or Yahoo Groups, but other Yahoo services may also be affected.