Add ignore certificate validity check for Nodemailer

[Add Sky]

Problem:
Even when specifying the "SMTP_secure: false" parameter in the configuration file, the connection to the local mail server gives the error "unable to verify the first certificate".

I would like to add the following parameter to the nodemailer connection:

tls: {
            // do not fail on invalid certs
            rejectUnauthorized: false
        },

[Maksim Eltyshev]

Hi! it'd be really nice to have this parameter.