certificate has expired [emails.send.exception] and other problems with smtp certificates

[silkroadnomad]

in many cases the smtp server to which we are sending our DOI-request emails, has an incorrect correct SSL-certificate. a workaround to this problem right now was to allow invalide SSL certificates from setting: process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0; in https://github.com/Doichain/dapp/blob/0.0.3/imports/startup/server/email-configuration.js#L29

this should be possible to be enabled in settings.json as an exception and not as right now as default. See:

• Meteor + Mail: https://docs.meteor.com/api/email.html
• Nodemailer (of Meteor): https://nodemailer.com/smtp/
• Quick Fix: https://stackoverflow.com/questions/45193873/hostname-ip-doesnt-match-certificates-altnames-meteor-js-email#45380144