-STARTTLS command establishes a secure communication session with email server, similarly to -SSL.
STARTTLS gets the information whether encrypted session is compatible with the server. Then, secured session is established right before transferring any sensitive data, such as credentials and message text itself. On the other hand, SSL establishes secure communication channel before sending any bits of information to the SMTP server.
The default port for TLS connection is 25. Usually -STARTTLS parameter is used with server authentication commands -AUTH, -USER and -PASS.
C:\>febootimail -SERVER smtp.mailserver.com -FROM firstname.lastname@example.org -TO email@example.com -USER john -PASS 3kr5$DrB -MSG Email sent through TLS enabled mail server -STARTTLS
Essentially, STARTTLS is very similar to SSL in general aspects. Some email clients uses SSL instead of STARTTLS.
C:\>febootimail -SUBJ "Gmail and STARTTLS" -SERVER smtp.gmail.com -STARTTLS -AUTH PLAIN -USER YourEmail@gmail.com -PASS *********** -FROM YourEmail@gmail.com -TO firstname.lastname@example.org -TEXT "This email is sent using Gmail's server. It is easy and secure!"
OpenSSL credit: This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit. (https://www.openssl.org/). This product includes cryptographic software written by Eric Young (email@example.com).
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