So when an e-mail is sent from an external source (for the first time), what actually happens to it? It's grey listed Link2ICT's end, but as far as I'm concerned it's sent my end. Why would any mail server re-send the same e-mail? I'm failing to understand how this concept works and clearly it's not just me.
Grey listing occurs when a external mail server tries to send mail to our mail servers, and this mail server has not sent mail to our mail servers before. The sending mail server is told that at the current time our mail server cannot service the request and to try again later.