msmtp:tldr:61c70

This command is composed of three parts:

1. echo "${Hello world}": The echo command is used to print a message or value, and "${Hello world}" is the message being printed in this case. However, the "${Hello world}" is an unusual syntax, as it is attempting to reference the value of a variable named "Hello world". Typically, variables are referenced without spaces and special characters. So, assuming that "Hello world" is the name of the variable, the correct syntax would be echo "${Hello world}".

2. |: This is known as a pipe operator. It is used to pass the output of the command preceding it as the input to the command that follows it. In this case, the output of the echo command will be passed as input to the msmtp command.

3. msmtp --account=${account_name} ${to@example-org}: This is the msmtp command with some additional options and arguments. msmtp is a command-line tool used for sending email messages.

• --account=${account_name} is an option that specifies the account to use for sending the email. The ${account_name} is likely a placeholder for the actual name of the account.
• ${to@example-org} is a placeholder for the email address of the recipient. Again, the actual email address should be used here instead.