SMTP is the acronym for Simple Mail Transfer Protocol, which is the protocol used for sending email. Anyone who has ever sent an email has used the SMTP protocol behind the scenes. Open mail relaying is when an SMTP server is configured in such a way that it lets anyone send email through it. The problem people have now is that open mail relaying is a thing of the past it is now much more difficult to find an SMTP server that will work for you. An SMTP relaying problem arises when you try to send an email through an SMTP server and find that you cannot, typically with an error message reading relaying mail to [email protected] is not allowed.
Relaying problems typically happen when you connect to the Internet from a different place than normal, for example if you try to use the same SMTP server from both work and home, or if you travel to different cities or countries. Students at universities often find that they cannot send emails using their universitys SMTP server when they are off campus. Office workers often find sending emails impossible when they are in their own home, or when they are in a hotel, Internet caf, or using an airports wireless network in a different...