SOFTware is HARD

According to the legal clauses in WhatsApp, such blocks have been made non-deterministic to protect privacy. However, by experimentation, you'd notice the following when you've been blocked: unable to see the "online" or "last seen" of the contact. Described here messages sent to the party does not get delivered - indicated by 1 tick instead of 2 unable to create a group with the party - An error message appears "Error while adding participant... not authorized to add this contact" The first 2 indicators are explained in WhatsApp's FAQ . Of interest is: We have made this intentionally ambiguous in order to protect your privacy when you block someone. Thus, we cannot tell you if you are being blocked by someone else, since this is a violation of that person's privacy  However, the 3 indicator above (not mentioned by WhatsApp) appears to be a very strong indicator that you've been blocked by the contact.

According to the HTTP specs, there are a number of HTTP codes used to redirect browser clients.   301 Moved Permanently : Permanent redirect. Document has moved permanently, future requests to use the redirected URL instead. Response is cacheable. Modern browsers change the HTTP method to a GET with the exception of IE (which preserves HTTP HEAD, DELETE method). 302 Found : Temporary redirect. To be superseded by 303 and 307. Response may be cached if headers allow for it. Most modern browsers treat this as 303 with the exception of IE (which treats it as 307). 303 See Other : Request should be redirected to a GET regardless of the original request method. The response must not be cached. Supported by all modern browsers. 307 Temporary Redirect : Temporary redirect. Request should be redirected to the redirected URL. The original request method is to be preserved and a POST request should be re-posted. Response may be cached if headers allow for it. Supported by all mod

A valid email address as of this form:   local-part @ domain-part In particular, the local part is required to be one of the following: dot-atom quoted string a combination of the above. E.g. my.name.is."Johannes Kuah"@example.com   Dot-Atom A string of ASCII characters excluding the following special characters :  whitespace ( ) < > @ , ; : \ " . [ ]   Quoted String A string of ASCII characters including the above special characters enclosed within normal ASCII quotation marks ("). However, the backslash \ and quotation mark " must also be preceded by a backslash \   References http://tools.ietf.org/html/rfc2822#section-3.4 http://tools.ietf.org/html/rfc3696#page-5