Simulating non-SNI browsers on SSL/TLS websites

Useful when you need to know whether the ssl/tls enabled website is accessible from ancient browsers and OS'es (taken from this stackoverflow answer):

openssl s_client -connect domain.com:443 
# ...output...
# ...proper response is something like
Verify return code: 0 (ok)
# ...invalid response is something like
Verify return code: 18 (self signed certificate)

See the wikipedia article for an explanation about SNI.