Scenario: You are a business person traveling around the world. You just got to your hotel room, turned on your laptop pc and are ready to answer to those very important emails that arrived while you were on the plane. So, you open your Outlook, Thunderbird or whatever email client you have, and start answering first the most important messages. Once you finish, you click on the "Send" button, totally confident and relieved because you needed that mail sent with extreme urgence. Oh no … what happened? You received one of these errors: smtp 550 error Unable to relay to user relaying denied mailbox unavailable or not local Server Error: 550 Error Number: 0x800CCC79 553 sorry, that domain is not in my list of allowed rcpthosts Server Error: 553 Error Number: 0x800CCC79
Why does this happen only when you are traveling?
Most Internet providers use two protocols to send and receive mails: SMTP and POP. SMTP (or Simple Mail Transfer Protocol) is the one used to send email out. When you are home, you are connected to your ISP network. Since you are already in that network, you will not have problems to use your ISP's SMTP server. But when you are in that hotel room you may have problems doing it, since you might be connecting from a different ISP network. So, it is pretty normal that you can not send emails from a different location
So, What Can You Do About That Relaying Denied Error?
There are many things to do. You could check if it is possible to enable the authentication when connecting to that SMTP server, so you can tell him "I am not a spammer" and be able to send emails wherever you want. You could also use web mail, but I am sure it is not the same, when you have all your emails well organized in your Outlook folders.
Going back to our scenario, maybe it is 1 am and you can not contact anyone to check about the SMTP authentication or webmail. Is there another option? A very valid solution to your email sending problems is: smtp2go. …