Sometimes there is no access on the website due to the ongoing technical work. This happens not so often because one of the leading post sites Runet. Therefore if this happens, it is likely a surprise to the administration, and the problem of trying to fix it fast enough. You need to try to visit the site, at least in a few minutes and check again. Even if the Inbox does not work, then for a time probably at least write that on the website is under maintenance and after some time, the work will be restored.
It is possible that the access denied is not on the site itself, but because of the redirect. Ie malicious software has changed the route of transition on a particular website. It happens quite often, especially if it is related to accounts of the postal services, mass portals, etc. Commonly these links contain a message like "send SMS to number so-and-so, to unlock". In order to fix the problem and get access to the mail service you need to go at: System drive – Windows - System32 - Drivers – Etc. There is a "hosts" file. You need to open it using Notepad and see the contents. The file should not contain any information, except: localhost. If it contains anything else, then you need to erase. Need to see it all very carefully, right and bottom often record additional information. For more expected all the content to highlight (press ctlr + a) then delete (del key). In net file to add localhost and save. Then restart the computer.
Sometimes that cause is a different kind of virus, and blocked your box because of his activities (e.g. the mass mailing of messages of a commercial nature). To solve the problem you need to check your operating system for viruses, and an effective means of protection: Kaspersky Internet Security paid or free CureIt. After that you need to write to support a letter explaining the problem and request access to the site.