Connect to port 443 and send some HTTP signals:
$ openssl s_client -connect example.com:443 [...snip...] Verify return code: 0 (ok) Extended master secret: no Max Early Data: 0 ---
You're now connected. If you wait too long, your connection will likely time out. View the default landing page of the site you've connected with:
GET / HTTP/1.1 HOST: example.com
In return, you get a dump of the HTML source of the default page (usually
index.html) in your terminal.
You can also use OpenSSL s_client for email servers using SSL. Before you can send credentials, you must encode your email username and passphrase into Base64. The easiest method I know is this Perl one-liner:
$ perl -MMIME::Base64 -e 'print encode_base64("myUserName");' $ perl -MMIME::Base64 -e 'print encode_base64("myPassPhrase");'
Take note of the results.
The s_client session, aside from authentication, is basically the same as a telnet session. You can find good telnet tutorials all over the Internet, and aside from sending your credentials, they apply to s_client.
Here's a copy-paste of an example session:
$ openssl s_client -starttls smtp -connect email.example.com:587 > ehlo example.com > auth login ##paste your user base64 string here#### ##paste your password base64 string here#### > mail from: email@example.com > rcpt to: firstname.lastname@example.org > data > Subject: Test 001 This is a test email. . > quit